FBO and Textures - opengl

I have attached two textures to an FBO. The first texture will be used to show a depth map. The second texture will show the object in a normal way.
If I do this, it works well and shows me the depth map.
GLuint atach0 = GL_DEPTH_ATTACHMENT;
glBindFramebuffer(GL_FRAMEBUFFER,fboBuffer);
glDrawBuffers(1,&atach0);
glClear(GL_DEPTH_BUFFER_BIT);
glViewport(0.0,0.0,640,480);
LProjection = glm::ortho(-10.0f,10.0f,-10.0f,10.0f,-500.0f,500.0f);
LView = glm::lookAt(glm::vec3(0.0f,15.0f,0.000001f),glm::vec3(0.0f,0.0f,0.0f),glm::vec3(0.0f,1.0f,0.0f));
LViewProjection = LProjection * LView;
glEnable(GL_DEPTH_TEST);
...CUBE3D
glBindFramebuffer(GL_FRAMEBUFFER,0);
glUniform1i(uniforTEX,0);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D,GL_DEPTH_MAP);
...DRAW-DEPTH-MAP!
glBindTexture(GL_TEXTURE_2D,0);
But if I do this, it only shows a white screen and the depth map is no longer visible.
GLuint atach0 = GL_DEPTH_ATTACHMENT;
glBindFramebuffer(GL_FRAMEBUFFER,fboBuffer);
glDrawBuffers(1,&atach0);
glClear(GL_DEPTH_BUFFER_BIT);
glViewport(auxrecX,auxrecY,auxrcAn,auxrcAl);
LProjection = glm::ortho(-10.0f,10.0f,-10.0f,10.0f,-500.0f,500.0f);
LView = glm::lookAt(glm::vec3(0.0f,15.0f,0.000001f),glm::vec3(0.0f,0.0f,0.0f),glm::vec3(0.0f,1.0f,0.0f));
LViewProjection = LProjection * LView;
glEnable(GL_DEPTH_TEST);
...CUBE3D
glBindFramebuffer(GL_FRAMEBUFFER,0);
GLuint atach1 = GL_COLOR_ATTACHMENT0;
glBindFramebuffer(GL_FRAMEBUFFER,fboBuffer);
glDrawBuffers(1,&atach1);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glViewport(0,0,640,480);
Projection = glm::perspective(45.0f,1.333333f,0.01f,1000.0f);
View = glm::lookAt(glm::vec3(0.0f,0.0f,3.0),glm::vec3(0.0f,0.0f,-15.0f),glm::vec3(0.0f,1.0f,0.0f));
ViewProjection = Projection * View;
glEnable(GL_DEPTH_TEST);
...CUBE3D
glBindFramebuffer(GL_FRAMEBUFFER,0);
glUniform1i(uniforTEX,0);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D,GL_DEPTH_MAP);
...DO NOT DRAW NOTHING
glBindTexture(GL_TEXTURE_2D,0);
I need to do it in that order. Because the first "pass" is for the use of the depth map in a shadow map. What am I doing wrong?

GL_DEPTH_ATTACHMENT is not valid for glDrawBuffers. glDrawBuffers of buffers into which outputs from the fragment shader data will be written.
When you do
GLuint atach0 = GL_DEPTH_ATTACHMENT;
glBindFramebuffer(GL_FRAMEBUFFER,fboBuffer);
then you'll get a GL_INVALID_ENUM error.
If you don't want to wirte to the depth map, then disable the depth test of use glDepthMask. The depth buffer attachment can't be switched on and off and it can't be uses somehow like a color buffer.
Further
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
will clear the depth buffer in any case.
I think there is a basic misunderstanding how the framebuffers for a shadow map have to be set up. You'll need a framebuffer for the shadow map only. This framebuffer has to have a depth buffer only.
You have to do mit somehow like this:
GLuint fboShadow; // framebuffer with depth buffer only (shadow map)
GLuint toShadowDepth; // texture which is the depth buffer of `fboShadow`
glBindFramebuffer(GL_FRAMEBUFFER, fboShadow);
GLuint atach0 = GL_NONE;
glDrawBuffers(1, &atach0);
glClear(GL_DEPTH_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);
glViewport(auxrecX, auxrecY, auxrcAn, auxrcAl);
// draw the shadow map to the depth buffer only
glBindFramebuffer(GL_FRAMEBUFFER, 0);
glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);
glViewport(0, 0, 640, 480);
glUniform1i(uniforTEX, 0);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, toShadowDepth);
// draw the geometry to the default framebuffer by using the depth map

Related

OpenGL - blend two textures on the same object

I want to apply two textures on the same object (actually just a 2D rectangle) in order to blend them. I thought I would achieve that by simply calling glDrawElements with the first texture, then binding the other texture and calling glDrawElements a second time. Like this:
//create vertex buffer, frame buffer, depth buffer, texture sampler, build and bind model
//...
glEnable(GL_BLEND);
glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ZERO);
glBlendEquation(GL_FUNC_ADD);
// Clear the screen
glClearColor(0, 0, 0, 0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// Bind our texture in Texture Unit 0
GLuint textureID;
//create or load texture
//...
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, textureID);
// Set our sampler to use Texture Unit 0
glUniform1i(textureSampler, 0);
// Draw the triangles !
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, (void*)0);
//second draw call
GLuint textureID2;
//create or load texture
//...
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, textureID2);
// Set our sampler to use Texture Unit 0
glUniform1i(textureSampler, 0);
// Draw the triangles !
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, (void*)0);
Unfortunately, the 2nd texture is not drawn at all and I only see the first texture. If I call glClear between the two draw calls, it correctly draws the 2nd texture.
Any pointers? How can I force OpenGL to draw on the second call?
As an alternative to the approach you followed so far I would like to suggest using two texture samplers within your GLSL shader and perform the blending there. This way, you would be done with just one draw call, thus reducing CPU/GPU interaction. To do so, just define to texture samplers in your shader like
layout(binding = 0) uniform sampler2D texture_0;
layout(binding = 1) uniform sampler2D texture_1;
Alternatively, you can use a sampler array:
layout(binding = 0) uniform sampler2DArray textures;
In your application, setup the textures and samplers using
enum Sampler_Unit{BASE_COLOR_S = GL_TEXTURE0 + 0, NORMAL_S = GL_TEXTURE0 + 2};
glActiveTexture(Sampler_Unit::BASE_COLOR_S);
glBindTexture(GL_TEXTURE_2D, textureBuffer1);
glTexStorage2D( ....)
glActiveTexture(Sampler_Unit::NORMAL_S);
glBindTexture(GL_TEXTURE_2D, textureBuffer2);
glTexStorage2D( ....)
Thanks to #tkausl for the tip.
I had depth testing enabled during the initialization phase.
// Enable depth test
glEnable(GL_DEPTH_TEST);
// Accept fragment if it closer to the camera than the former one
glDepthFunc(GL_LESS);
The option needs to be disabled in my case, for the blend operation to work.
//make sure to disable depth test
glDisable(GL_DEPTH_TEST);

How to set a texture as background in OpenGL?

I want to make a program that shows the earth with a space texture as the background.
The earth is a 3D Uniform with a earth texture (.bmp).
The space with the stars is a texture (.bmp).
I have summarized what I have to do:
Create a new Model Matrix
Position it at the same place where the camera is
Disable depth test before drawing
Reverse culling
This is the Load function:
void load(){
//Load The Shader
Shader simpleShader("src/shader.vert", "src/shader.frag");
g_simpleShader = simpleShader.program;
// Create the VAO where we store all geometry (stored in g_Vao)
g_Vao = gl_createAndBindVAO();
//Create vertex buffer for positions, colors, and indices, and bind them to shader
gl_createAndBindAttribute(&(shapes[0].mesh.positions[0]), shapes[0].mesh.positions.size() * sizeof(float), g_simpleShader, "a_vertex", 3);
gl_createIndexBuffer(&(shapes[0].mesh.indices[0]), shapes[0].mesh.indices.size() * sizeof(unsigned int));
gl_createAndBindAttribute(uvs, uvs_size, g_simpleShader, "a_uv", 2);
gl_createAndBindAttribute(normal, normal_size, g_simpleShader, "a_normal", 2);
//Unbind Everything
gl_unbindVAO();
//Store Number of Triangles (use in draw())
g_NumTriangles = shapes[0].mesh.indices.size() / 3;
//Paths of the earth and space textures
Image* image = loadBMP("assets/earthmap1k.bmp");
Image* space = loadBMP("assets/milkyway.bmp");
//Generate Textures
glGenTextures(1, &texture_id);
glGenTextures(1, &texture_id2);
//Bind Textures
glBindTexture(GL_TEXTURE_2D, texture_id);
glBindTexture(GL_TEXTURE_2D, texture_id2);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
//We assign your corresponding data
glTexImage2D(GL_TEXTURE_2D,1,GL_RGB,image->width, image->height,GL_RGB,GL_UNSIGNED_BYTE,image->pixels);
glTexImage2D(GL_TEXTURE_2D,1,GL_RGB,space->width, space->height,GL_RGB,GL_UNSIGNED_BYTE,space->pixels);
}
This is the Draw function:
void draw(){
//1. Enable/Disable
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glDisable(GL_DEPTH_TEST);
glEnable(GL_CULL_FACE);
glCullFace(GL_FRONT);
//2. Shader Activation
glUseProgram(g_simpleShader);
//3. Get All Uniform Locations
//Space:
GLuint model_loc2 = glGetUniformLocation (g_simpleShader, "u_model");
GLuint u_texture2 = glGetUniformLocation(g_simpleShader, "u_texture2");
GLuint u_light_dir2 = glGetUniformLocation(g_simpleShader,"u_light_dir2");
//Earth
GLuint model_loc = glGetUniformLocation(g_simpleShader, "u_model");
GLuint projection_loc = glGetUniformLocation(g_simpleShader, "u_projection");
GLuint view_loc = glGetUniformLocation(g_simpleShader, "u_view");
GLuint u_texture = glGetUniformLocation(g_simpleShader, "u_texture");
GLuint u_light_dir = glGetUniformLocation(g_simpleShader, "u_light_dir");
//4. Get Values From All Uniforms
mat4 model_matrix2 = translate(mat4(1.0f), vec3(1.0f,-3.0f,1.0f));
mat4 model_matrix = translate(mat4(1.0f),vec3(0.0f,-0.35f,0.0f);
mat4 projection_matrix = perspective(60.0f,1.0f,0.1f,50.0f);
mat4 view_matrix = lookAt(vec3( 1.0f, -3.0f, 1.0f),vec3(0.0f, 0.0f, 0.0f), vec3(0.0f, 1.0f, 0.0f)glm::vec3(0,1,0));
//5. Upload Uniforms To Shader
glUniformMatrix4fv(model_loc2, 1, GL_FALSE, glm::value_ptr(model_matrix2));
glUniformMatrix4fv(model_loc, 1, GL_FALSE, glm::value_ptr(model_matrix));
glUniformMatrix4fv(projection_loc, 1, GL_FALSE, glm::value_ptr(projection_matrix));
glUniformMatrix4fv(view_loc, 1, GL_FALSE, glm::value_ptr(view_matrix));
glUniform1i(u_texture, 0);
glUniform3f(u_light_dir, g_light_dir.x, g_light_dir.y, g_light_dir.z);
glUniform1i(u_texture2, 1);
glUniform3f(u_light_dir2, g_light_dir.x, g_light_dir.y, g_light_dir.z);
//6. Activate Texture Unit 0 and Bind our Texture Object
glActiveTexture(GL_TEXTURE0);
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, texture_id);
glBindTexture(GL_TEXTURE_2D, texture_id2);
//7. Bind VAO
gl_bindVAO(g_Vao);
//8. Draw Elements
glDrawElements(GL_TRIANGLES, 3 * g_NumTriangles, GL_UNSIGNED_INT, 0);
}
Also I have two Fragment Shaders:
The first one returns this:
fragColor = vec4(final_color, 1.0);
The second one returns this:
fragColor = vec4(texture_color.xyz, 1.0);
Also the Vertex Shader returns the position of the vertex:
gl_Position = u_projection * u_view * u_model * vec4( a_vertex , 1.0 );
When I compile, it only shows the earth while it should show the earth and the space as background. I have reviewed the code several times but I can not find out what it is.
Suposed result:
My Result
If I see it right among other things you are wrongly binding textures
glActiveTexture(GL_TEXTURE0);
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, texture_id);
glBindTexture(GL_TEXTURE_2D, texture_id2);
should be:
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, texture_id);
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, texture_id2);
but I prefer that last set active units is 0 ...
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, texture_id2);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, texture_id);
that will save you a lot of troubles when you start combine code with single texture unit code ... Also hope you are properly unbinding the used texture units for the same reasons...
You got ugly seam on the edge 0/360deg of longitude
this might be caused by wrongly computed normal for lighting, wrong not seamless texture or just by forgeting to duplicate the edge points with correct texture coordinates for the last patch. See:
Applying map of the earth texture a Sphere
You can also add atmosphere,bump map, clouds to your planet:
Bump-map a sphere with a texture map
Andrea is right...
set matrices as unit matrix and render (+/-)1.0 rectangle at z=0.0 +/- aspect ratio correction without depth test, face culling and depth write ... That way you will avoid jitter and flickering stuff due to floating point errors.
Skybox is better but there are also other options to enhance
Is it possible to make realistic n-body solar system simulation in matter of size and mass?
and all the sublinks in there especially stars. You can combine skybox and stellar catalog together and much much more...

Deferred Rendering Skybox OpenGL

I've just implemented deferred rendering and am having trouble getting my skybox working. I try rendering my skybox at the very end of my rendering loop and all I get is a black screen. Here's the rendering loop:
//binds the fbo
gBuffer.Bind();
//the shader that writes info to gbuffer
geometryPass.Bind();
glDepthMask(GL_TRUE);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);
glDisable(GL_BLEND);
//draw geometry
geometryPass.SetUniform("model", transform.GetModel());
geometryPass.SetUniform("mvp", camera.GetViewProjection() * transform.GetModel());
mesh3.Draw();
geometryPass.SetUniform("model", transform2.GetModel());
geometryPass.SetUniform("mvp", camera.GetViewProjection() * transform2.GetModel());
sphere.Draw();
glDepthMask(GL_FALSE);
glDisable(GL_DEPTH_TEST);
glEnable(GL_BLEND);
glBlendEquation(GL_FUNC_ADD);
glBlendFunc(GL_ONE, GL_ONE);
glBindFramebuffer(GL_FRAMEBUFFER, 0);
glClear(GL_COLOR_BUFFER_BIT);
//shader that calculates lighting
pointLightPass.Bind();
pointLightPass.SetUniform("cameraPos", camera.GetTransform().GetPosition());
for (int i = 0; i < 2; i++)
{
pointLightPass.SetUniformPointLight("light", pointLights[i]);
pointLightPass.SetUniform("mvp", glm::mat4(1.0f));
//skybox.GetCubeMap()->Bind(9);
quad.Draw();
}
//draw skybox
glEnable(GL_DEPTH_TEST);
skybox.Render(camera);
window.Update();
window.SwapBuffers();
The following is the skybox's render function
glCullFace(GL_FRONT);
glDepthFunc(GL_LEQUAL);
m_transform.SetPosition(camera.GetTransform().GetPosition());
m_shader->Bind();
m_shader->SetUniform("mvp", camera.GetViewProjection() * m_transform.GetModel());
m_shader->SetUniform("cubeMap", 0);
m_cubeMap->Bind(0);
m_cubeMesh->Draw();
glDepthFunc(GL_LESS);
glCullFace(GL_BACK);
And here is the skybox's vertex shader:
layout (location = 0) in vec3 position;
out vec3 TexCoord;
uniform mat4 mvp;
void main()
{
vec4 pos = mvp * vec4(position, 1.0);
gl_Position = pos.xyww;
TexCoord = position;
}
The skybox's fragment shader just sets the output color to texture(cubeMap, TexCoord).
As you can see from the vertex shader, I'm setting the position's z component to be w so that it will always have a depth of 1. I am also setting the depth function to be GL_LEQUAL so that it will fail the depth test. Should this not only draw the skybox in places where other objects weren't already drawn? Why does it result in a black screen?
I know I have set up the skybox correctly because if I just draw the skybox by itself it shows up just fine.
I can briefly see for a split second the geometry that should be drawn before the skybox is drawn on top of everything.
Since you're using double buffering, seeing different things must be due to a different frame being drawn. The depth buffer in the default framebuffer isn't being cleared, which I believe is the cause of the temporal instability at least.
In your case, you want the default depth buffer to be the same as the GBuffer when you draw the skybox. A quick way to achieve this is with glBlitFramebuffer, also avoiding the need to clear it:
glBindFramebuffer(GL_READ_FRAMEBUFFER, gbuffer);
glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
glBlitFramebuffer(..., GL_DEPTH_BUFFER_BIT, ...);
Now to explain the black screen when the skybox fills the screen. Without the depth test, of course the skybox just draws. With the depth test, the skybox still draws on the first frame, but shortly after the second frame clears only the colour buffer. The depth buffer still contains stale skybox values so it does not get re-draw for this frame and you're left with black...
However your geometry pass draws without depth testing enabled, so this should still be visible even if the skybox isn't. Also this would only happen with GL_LESS and you have GL_LEQUAL. And you have glDepthMask false, which means nothing should write to the default depth buffer in your code. This points to the depth buffer containing other values, perhaps uninitialized, but in my experience it's initially zero. Also this still happens when the skybox doesn't fill the screen, drawn as a cube away from the camera, which blows away that argument. Now, perhaps if the geometry failed to draw in the second frame that would explain it. For that matter blatant driver bugs would too, but I'm not seeing any problems in the given code.
TLDR: Many unexplained things, so **I tried it myself and can't reproduce your problem...
Here's a quick example based on your code and it works fine for me...
(green sphere is the geometry, red cube is the skybox)
gl_Position = pos:
Note the yellow from additive blending even if the skybox is drawn over the top. I would have thought you'd be seeing this too.
gl_Position = pos.xyww:
Now for the code...
//I haven't enabled back face culling, but that shouldn't affect anything
//binds the fbo
fbo.bind();
//the shader that writes info to gbuffer
//geometryPass.Bind(); //fixed pipeline for now
glDepthMask(GL_TRUE);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);
glDisable(GL_BLEND);
glColor3f(0,1,0);
fly.uploadCamera(); //glLoadMatrixf
sphere.draw();
glDepthMask(GL_FALSE);
glDisable(GL_DEPTH_TEST);
glEnable(GL_BLEND);
glBlendEquation(GL_FUNC_ADD);
glBlendFunc(GL_ONE, GL_ONE);
fbo.unbind(); //glBindFramebuffer(GL_FRAMEBUFFER, 0);
glClear(GL_COLOR_BUFFER_BIT);
//shader that calculates lighting
drawtex.use();
//pointLightPass.SetUniform("cameraPos", camera.GetTransform().GetPosition());
drawtex.set("tex", *(Texture2D*)fbo.colour[0]);
for (int i = 0; i < 2; i++)
{
//pointLightPass.SetUniformPointLight("light", pointLights[i]);
//pointLightPass.SetUniform("mvp", glm::mat4(1.0f));
//skybox.GetCubeMap()->Bind(9);
drawtex.set("modelviewMat", mat44::identity());
quad.draw();
}
drawtex.unuse();
//draw skybox
glEnable(GL_DEPTH_TEST);
glBindFramebuffer(GL_READ_FRAMEBUFFER, fbo);
glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
glBlitFramebuffer(0, 0, fbo.size.x, fbo.size.y, 0, 0, fbo.size.x, fbo.size.y, GL_DEPTH_BUFFER_BIT, GL_NEAREST);
glBindFramebuffer(GL_FRAMEBUFFER, 0);
//glCullFace(GL_FRONT);
glDepthFunc(GL_LEQUAL);
//m_transform.SetPosition(camera.GetTransform().GetPosition());
skybox.use();
skybox.set("mvp", fly.camera.getProjection() * fly.camera.getInverse() * mat44::translate(1,0,0));
//m_shader->SetUniform("mvp", camera.GetViewProjection() * m_transform.GetModel());
//m_shader->SetUniform("cubeMap", 0);
//m_cubeMap->Bind(0);
cube.draw();
skybox.unuse();
glDepthFunc(GL_LESS);
//glCullFace(GL_BACK);
//window.Update();
//window.SwapBuffers();

OpenGL stencil buffer concave polygon

I'm trying to do this example.
I couldn't understand how it works still and I'm having difficulties in visualizing how the code would look like.
I stumbled upon this post which was the closest I think I could find.
From the redbook link, how can I do a "two-pass algorithm" to get the desired output? How do I use GL_INVERT and check if the pixel is covered even number of times?
I somehow managed to understand how the stencil works for the concave polygon but my problem now is the polygon is being rendered incorrectly.
http://img.photobucket.com/albums/v442/ardo/ScreenShot2013-12-30at24155PM.png
The location of where I am drawing this is in a framebuffer which is set up like this:
//multisample
glGenRenderbuffersEXT(1, &colorBuffer);
glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, colorBuffer);
glRenderbufferStorageMultisampleEXT(GL_RENDERBUFFER_EXT, multisampling, GL_RGBA,800, 600);
//multi sample depth
glGenRenderbuffersEXT(1, &depthBuffer);
glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, depthBuffer);
glRenderbufferStorageMultisampleEXT(GL_RENDERBUFFER_EXT, multisampling, GL_DEPTH24_STENCIL8, 800, 600);
//multisamplefbo
glGenFramebuffersEXT(1, &mFBO);
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, mFBO);
glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_RENDERBUFFER_EXT, colorBuffer);
glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_STENCIL_ATTACHMENT, GL_RENDERBUFFER_EXT, depthBuffer);
Then my drawing code is:
glEnable(GL_STENCIL_TEST);
glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
glStencilFunc(GL_ALWAYS, 0x1, 0x1);
glStencilOp(GL_KEEP, GL_INVERT, GL_INVERT);
glBegin(GL_TRIANGLE_FAN);
glVertex3f(1.396900,3.130690,0);
glVertex3f(2.034830,2.466900,0);
glVertex3f(2.486338,2.441036,0);
glVertex3f(2.802204,2.437803,0);
glVertex3f(2.910181,2.447098,0);
glVertex3f(2.957240,2.466900,0);
glVertex3f(3.019335,2.552570,0);
glVertex3f(3.130733,2.673799,0);
glVertex3f(3.284830,2.828970,0);
glVertex3f(3.474490,3.087590,0);
glVertex3f(4.319320,2.596210,0);
glVertex3f(4.508980,2.147930,0);
glVertex3f(4.714798,1.866680,0);
glVertex3f(4.907215,1.620586,0);
glVertex3f(5.101651,1.397930,0);
glVertex3f(5.186114,1.317364,0);
glVertex3f(5.254869,1.269024,0);
glVertex3f(5.302510,1.261700,0);
glVertex3f(5.323633,1.304180,0);
glVertex3f(5.312832,1.405254,0);
glVertex3f(5.264703,1.573711,0);
glVertex3f(5.173841,1.818340,0);
glVertex3f(5.034840,2.147930,0);
glVertex3f(4.875695,2.492816,0);
glVertex3f(4.727900,2.780675,0);
glVertex3f(4.591307,3.016304,0);
glVertex3f(4.465765,3.204503,0);
glVertex3f(4.351127,3.350070,0);
glVertex3f(4.247241,3.457803,0);
glVertex3f(4.153958,3.532502,0);
glVertex3f(4.071129,3.578965,0);
glVertex3f(3.998605,3.601990,0);
glVertex3f(3.936235,3.606376,0);
glVertex3f(3.841363,3.578427,0);
glVertex3f(3.766900,3.510000,0);
glVertex3f(2.974490,3.458280,0);
glVertex3f(2.672770,2.958280,0);
glVertex3f(2.379670,3.070350,0);
glVertex3f(1.853810,3.303110,0);
glVertex3f(1.396910,3.303110,0);
glVertex3f(1.396910,3.130690,0);
glVertex3f(1.396900,3.130690,0);
glVertex3f(1.396900,3.130690,0);
glEnd();
glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
glStencilFunc(GL_EQUAL, 0x1, 0x1);
glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
glColor3f(1,0,1);
glBegin(GL_TRIANGLE_FAN);
glVertex3f(1.396900,3.130690,0);
glVertex3f(2.034830,2.466900,0);
glVertex3f(2.486338,2.441036,0);
glVertex3f(2.802204,2.437803,0);
glVertex3f(2.910181,2.447098,0);
glVertex3f(2.957240,2.466900,0);
glVertex3f(3.019335,2.552570,0);
glVertex3f(3.130733,2.673799,0);
glVertex3f(3.284830,2.828970,0);
glVertex3f(3.474490,3.087590,0);
glVertex3f(4.319320,2.596210,0);
glVertex3f(4.508980,2.147930,0);
glVertex3f(4.714798,1.866680,0);
glVertex3f(4.907215,1.620586,0);
glVertex3f(5.101651,1.397930,0);
glVertex3f(5.186114,1.317364,0);
glVertex3f(5.254869,1.269024,0);
glVertex3f(5.302510,1.261700,0);
glVertex3f(5.323633,1.304180,0);
glVertex3f(5.312832,1.405254,0);
glVertex3f(5.264703,1.573711,0);
glVertex3f(5.173841,1.818340,0);
glVertex3f(5.034840,2.147930,0);
glVertex3f(4.875695,2.492816,0);
glVertex3f(4.727900,2.780675,0);
glVertex3f(4.591307,3.016304,0);
glVertex3f(4.465765,3.204503,0);
glVertex3f(4.351127,3.350070,0);
glVertex3f(4.247241,3.457803,0);
glVertex3f(4.153958,3.532502,0);
glVertex3f(4.071129,3.578965,0);
glVertex3f(3.998605,3.601990,0);
glVertex3f(3.936235,3.606376,0);
glVertex3f(3.841363,3.578427,0);
glVertex3f(3.766900,3.510000,0);
glVertex3f(2.974490,3.458280,0);
glVertex3f(2.672770,2.958280,0);
glVertex3f(2.379670,3.070350,0);
glVertex3f(1.853810,3.303110,0);
glVertex3f(1.396910,3.303110,0);
glVertex3f(1.396910,3.130690,0);
glVertex3f(1.396900,3.130690,0);
glVertex3f(1.396900,3.130690,0);
glEnd();
glDisable(GL_STENCIL_TEST);
The way I have my multisampling set up is here (This is before the drawing is written)
[self checkError];
glEnable(GL_DEPTH_TEST);
[self checkError];
glDepthMask(GL_TRUE);
[self checkError];
glDepthFunc(GL_LESS);
[self checkError];
glClearDepth(10000.0);
[self checkError];
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
[self checkError];
if(multisampling != 0){
//Set multisampled framebuffer
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, mFBO);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
//Antialiasing functions
glEnable (GL_POLYGON_SMOOTH);
glEnable (GL_BLEND);
glBlendFunc (GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glHint (GL_POLYGON_SMOOTH_HINT, GL_NICEST);
glLineWidth (1.5);
}
glDisable(GL_CULL_FACE);
And my blit call:
glBindFramebufferEXT(GL_READ_FRAMEBUFFER_EXT, mFBO);
glBindFramebufferEXT(GL_DRAW_FRAMEBUFFER_EXT, currentFramebuffer);
glBlitFramebuffer(0, 0, 800, 600, 0, 0, 800, 600, GL_COLOR_BUFFER_BIT, GL_NEAREST);
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, mFBO);
glReadBuffer(GL_COLOR_ATTACHMENT0_EXT);
glBindFramebufferEXT(GL_DRAW_FRAMEBUFFER_EXT, currentFramebuffer);
glBindFramebufferEXT(GL_READ_FRAMEBUFFER_EXT, currentFramebuffer);
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, currentFramebuffer);
What don't you get? The example starts out with a stencil buffer cleared to 0x00 and each time you draw a fragment (whether it passes or fails a depth/stencil test) it performs a bitwise inversion of the stencil buffer (e.g. ~0x00 --> 0xff). If you do this an odd number of times, the stencil buffer will be non-zero, but if you have an even number of fragments it will be zero.
Some things that might be confusing are the use of 1 as the bitmask for the stencil test and the stencil op in the second pass. This effectively limits the test to a single bit. In other words, the bit flipping I mentioned earlier will only happen for bit 1. Thus, you can actually simplify your test for even/odd to a test of a single bit... if the stencil buffer stores a value of 1 then you drew an odd number of fragments. If it stores a value of 0 then you drew an even number.
The second pass in your example actually does the exact stencil test I described. It tests the stencil buffer for 1 and fails the stencil test if the first bit != 1.
// The stencil op below is a convoluted way of clearing the stencil buffer
glStencilOp (GL_ZERO, GL_ZERO, GL_ZERO);
glStencilFunc (GL_EQUAL, 1, 1); // Test: (Stencil & 1) == 1

ShadowMap confuse

I am confused about shadow mapping. Here's what I've understood (folowing steps are not working:) )
How to get profit (please don't get confused about the code, it is roughly because I write on Java):
1. Create empty depthTexture (mine is 1024x1024) with parameters
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE, GL_COMPARE_R_TO_TEXTURE) and
glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, width, height, 0, GL_DEPTH_COMPONENT, GL_FLOAT, GL_NULL)
2. Create FBO and attach that texture to it
glFramebufferTexture(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, depthTexture, 0)
3. Setup new projection and view matrix for lighting camera
I used the same as my main camera just with another coords, because scene looks better in it (I tried it out, so there's no problem... I guess ..).
4. Create new little shader to determinate gl_Position for FBO and modify the main shader with fancy stuff (bias matrix * lightCamera matrix * vertex, sampler2Dshadow and more)
5. Of course uniform everything and do something.
And now RENDER LOOP
1. Of course uniform everything and do something(again).
2. Bind FBO, bind little shader, glViewport(0, 0, 1024, 1024), colorMask to false, clear depth buffer, glCullFace(GL_FRONT), glBindTexture(GL_TEXTURE_2D, 0)
3. Render everything using only vertex position attribs completely for nothing
4. Unbind FBO, rebind program to main shader (that one with fancy stuff), glViewport, enable colorMask, glCullFace(GL_BACK)
5. Render the scene normally without even thinking about "How the hell main shader gonna get sampler2DShadow because we dont bind it, dont uniform it, and don't even touch it"
6. Watch countless glitches, bugs and pixel orgy
Actually I tried to uniform depthTexture to sampler, but I've got black screen only. And even if I dont render FBO, I get the same picture when I do that.
Can someone explain, what am I missing?
I feel like shader uses diffuse texture twice: as a diffuse texture and as a depthTexture, but I don't know how to give it that depthTexture.
here is a good link to read: http://www.opengl-tutorial.org/intermediate-tutorials/tutorial-16-shadow-mapping/
and here: http://www.paulsprojects.net/tutorials/smt/smt.html (although the second link uses old fixed function opengl)
in general:
create one depth texture
attach this texture to FBO
bind FBO, setup proper viewport
render scene from light pos, save only depth values to your texture
unbind FBO and setup final scene vieport and camera position
render scene normally using shadow test (sampler2DShadow)
you can render your depth map always (in render loop) or only when light pos changes.
I do not know why you are rendering you scene normally twice... are you using Z-prepass, or something? just try the basic version I think.
my old code with shadow maps:
void RenderShadowMap() {
currDepth->Bind();
glClear(GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gLightCam.SetProjectionMatrix();
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gLightCam.SetViewMatrix();
glColorMask(false, false, false, false);
glUseProgram(0); // draw without any shaders... just default depth
glEnable(GL_POLYGON_OFFSET_FILL);
glPolygonOffset(offFactor, offUnits);
SimpleScene(false); // floor does not cast shadow so do not render it
glDisable(GL_POLYGON_OFFSET_FILL);
glColorMask(true, true, true, true);
}
render scene:
// compose shadow matrix:
MATRIX4X4 bias(0.5f, 0.0f, 0.0f, 0.0f,
0.0f, 0.5f, 0.0f, 0.0f,
0.0f, 0.0f, 0.5f, 0.0f,
0.5f, 0.5f, 0.5f, 1.0f);
MATRIX4X4 *invCam = gSphericalCam.GetInvViewMatrix();
MATRIX4X4 smMat = (*gLightCam.GetViewProjMatrix()) * (*invCam);
gShaderProgramManager->GetProgram("shadow")->Use();
gShaderProgramManager->GetProgram("shadow")->SetMatrix("shadowMat", &smMat);
gShaderProgramManager->GetProgram("shadow")->SetBool("useShadow", currCam != &gLightCam && useShadow);
gShaderProgramManager->GetProgram("shadow")->SetFloat("shadowMapSize", (float)currDepth->GetWidth());
glActiveTexture(GL_TEXTURE0);
glEnable(GL_TEXTURE_2D);
glColor3f(1.0f, 1.0f, 1.0f);
gTextureManager->Bind("default");
glActiveTexture(GL_TEXTURE1);
currDepth->BindDepthAsTexture();
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE_ARB, GL_COMPARE_R_TO_TEXTURE_ARB);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_FUNC_ARB, GL_LEQUAL);
SimpleScene();