I just started working with OpenGL, but I ran into a problem after implementing a Font system.
My plan is to simply visualize several Pathfinding Algorithms.
Currently OpenGL gets set up like this (OnSize gets called once on window creation manually):
void GLWindow::OnSize(GLsizei width, GLsizei height)
{
// set size
glViewport(0,0,width,height);
// orthographic projection
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0.0,width,height,0.0,-1.0,1.0);
glMatrixMode(GL_MODELVIEW);
m_uiWidth = width;
m_uiHeight = height;
}
void GLWindow::InitGL()
{
// enable 2D texturing
glEnable(GL_TEXTURE_2D);
// choose a smooth shading model
glShadeModel(GL_SMOOTH);
// set the clear color to black
glClearColor(0.0, 0.0, 0.0, 0.0);
glEnable(GL_ALPHA_TEST);
glAlphaFunc(GL_GREATER, 0.0f);
}
In theory I don't need blending, because I will only use untextured Quads to visualize obstacles and line etc to draw paths... So everything will be untextured, except the fonts...
The Font Class has a push and pop function, that look like this (if I remember right my Font system is based on a NeHe Tutorial that I was following quite a while ago):
inline void GLFont::pushScreenMatrix()
{
glPushAttrib(GL_TRANSFORM_BIT);
GLint viewport[4];
glGetIntegerv(GL_VIEWPORT, viewport);
glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();
glOrtho(viewport[0],viewport[2],viewport[1],viewport[3], -1.0, 1.0);
glPopAttrib();
}
inline void GLFont::popProjectionMatrix()
{
glPushAttrib(GL_TRANSFORM_BIT);
glMatrixMode(GL_PROJECTION);
glPopMatrix();
glPopAttrib();
}
So the Problem:
If I don't draw a Text I can see the Quads I want to draw, but they are quite dark, so there must be something wrong with my general OpenGL Matrix Properties.
If I draw Text (so the font related push and pop functions get called) I can't see any Quads.
The question:
How do I solve this problem and some background information why this happened would also be nice, because I am still a beginner/student, who just started.
If your quads are untextured, you will run into undefined behaviour. What will probably happen is that any previous texture will be used, and the colour at point (0,0) will be used, which could be what is causing them to be invisible.
Really, you need to disable texturing before trying to draw untextured quads using glDisable(GL_TEXTURE_2D). Again, if you don't, it'll just use the previous texture and texture co-ordinates, which without seeing your draw() loop, I'm assuming to be undefined.
Related
I can't figure out how to use pangolin to display 2D openGL graphics.
I'm am in internship in the research department of a school.
I am very novice at OpenGl and Pangolin.
I'm trying to add a monitoring window to an open_source program so that it is more user-friendly. This program is ORB_SLAM2, and it already uses pangolin as an openGL display manager. It has already some windows opening with panels and 3d openGL displays like thisby this piece of code
void Viewer::Run()
{
//...
pangolin::CreateWindowAndBind("ORB-SLAM2: Map Viewer",1024,768);
// 3D Mouse handler requires depth testing to be enabled
glEnable(GL_DEPTH_TEST);
// Issue specific OpenGl we might need
glEnable (GL_BLEND);
glBlendFunc (GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
pangolin::CreatePanel("menu").SetBounds(0.0,1.0,0.0,pangolin::Attach::Pix(175));
// ... define elements of the menu (not important)
// Define Camera Render Object (for view / scene browsing)
pangolin::OpenGlRenderState s_cam(
pangolin::ProjectionMatrix(1024,768,mViewpointF,mViewpointF,512,389,0.1,1000),
pangolin::ModelViewLookAt(mViewpointX,mViewpointY,mViewpointZ, 0,0,0,0.0,-1.0, 0.0));
// Add named OpenGL viewport to window and provide 3D Handler
pangolin::View& d_cam = pangolin::CreateDisplay()
.SetBounds(0.0, 1.0, pangolin::Attach::Pix(175), 1.0, -1024.0f/768.0f)
.SetHandler(new pangolin::Handler3D(s_cam));
pangolin::OpenGlMatrix Twc;
Twc.SetIdentity();
//...
while(1)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
mpMapDrawer->GetCurrentOpenGLCameraMatrix(Twc);
//...
d_cam.Activate(s_cam);
glClearColor(1.0f,1.0f,1.0f,1.0f);
mpMapDrawer->DrawCurrentCamera(Twc);
if(menuShowKeyFrames || menuShowGraph)
mpMapDrawer->DrawKeyFrames(menuShowKeyFrames,menuShowGraph);
if(menuShowPoints)
mpMapDrawer->DrawMapPoints();
pangolin::FinishFrame();
//...
}
So I tried to copy that and remove the 3D handling part of it like this
void Monitor::Run()
{
//...
pangolin::CreateWindowAndBind("ORB-SLAM2: Monitoring",1024,768);
// Issue specific OpenGl we might need
glEnable (GL_BLEND);
glBlendFunc (GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
pangolin::View& menu = pangolin::CreatePanel("vars").SetBounds(0.0,1.0,0.0,pangolin::Attach::Pix(175));
//...
// Add named OpenGL viewport to window
pangolin::View& graph = pangolin::CreateDisplay()
.SetBounds(0.0, 1.0, pangolin::Attach::Pix(175), 1.0, 1024.0f/768.0f);
while (1){
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
graph.Activate();
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
// 2D Basic test shape
glBegin(GL_QUADS);
glColor3f(0.4f, 0.05f, 0.05f);
glVertex2f(-0.5, 0.8f);
glVertex2f(-0.8f, -0.8f);
glVertex2f(0.8f, -0.8f);
glVertex2f(0.8f, 0.8f); glEnd();
pangolin::FinishFrame();
}
}
But The 2D Shape isn't apearing, it only shows the background color
I tried the followings:
Removing the Panel: it makes the shape appear but I want to keep the panel.
Changing zorders of the menu and the shape in both orders, didn't change anything
Not enclosing it in an infinite while loop: Both panel and shape appeared but obviously it is a static image. But it appears the render works the first call of FinishFrame() and then it doesn't anymore.
And other stuffs but i can't list it all here.
I'm wandering if it is because I didn't create OpenGlRenderState Object, But I don't understand why I would need it for 2D Rendering from my understanding of OpenGL and Pangolin.
I hope you guys can help me.
So I'm trying to render a basic overlay onto my 3D scene, and currently I can either have the 3D scene or the 2D overlay, I cant work out how to get both
In my main method, where render is called, I moved specific render functions to manager classes, so in the main render I call :
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);
glEnable(GL_COLOR_MATERIAL);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-aspect, aspect, -1, 1, -10, 10);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
material.setColour(new Vector3f(1,1,1));
sLight.getPointLight().setPosition(camera.getPosition());
sLight.setDirection(camera.getForward());
DayCycle.getInstance().update(Time.getDelta());
shader.updateUniforms(transform.getTransformation(), transform.getProjectedTransformation(), material);
//material is a wrapper class for textures and specular value etc
//transform is a matrix wrapper for getting projected transformations, taking the camera position when its created
WorldManager.renderAll(true); //true denotes yes to wireframe mode
InterfaceManager.renderAll();
glfwSwapBuffers(window);
glfwPollEvents();
If i comment out WorldManager.renderAll(), I get the little 2d square in the right part of the screen, If i dont comment it, I get the world render but no little square
WorldManager.renderAll()
public static void renderAll(boolean wireframeMode)
{
RendererUtils.setWireframeMode(wireframeMode);
for (String s : chunks.keySet())
{
Chunk actingChunk = chunks.get(s);
Transform transform = new Transform();
Shader shader = PhongShader.getInstance();
transform.setTranslation(new Vector3f(actingChunk.getLocation().getX() * (Chunk.ChunkSize),0.0f, actingChunk.getLocation().getY() * (Chunk.ChunkSize)));
transform.setScale(1.0f, 50f, 1.0f);
shader.updateUniforms(transform.getTransformation(), transform.getProjectedTransformation(), actingChunk.getMaterial());
shader.bind();
actingChunk.getMesh().draw();
//transform.setRotation(new Vector3f(0,0,0));
}
}
InterfaceManager.renderAll()
public static void renderAll()
{
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, width, 0, height, -10, 10);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glDisable(GL_CULL_FACE);
glDisable(GL_DEPTH_TEST);
RendererUtils.setWireframeMode(false);
for (Interface i : interfaces)
{
Transform transform = new Transform();
transform.setTranslation(new Vector3f(0,0,0));
InterfaceShader.getInstance().updateUniforms(transform.getProjectedTransformation());
InterfaceShader.getInstance().bind();
i.getMesh().draw();
}
glEnable(GL_DEPTH_TEST);
glEnable(GL_CULL_FACE);
}
When I have WorldManager.renderAll() uncommented, i get a nice sea of triangles (as its meant to look) but no 2D square
With it commented, I get a nice little square where its meant to be and nothing else
Shaders are here : https://pastebin.com/xWaWhQHy because I felt this post was getting too long to have them inlined
What's my problem? I cant figure out where it is
Edit : If i've missed any pertinent code, tell me and i'll upload it to a pastebin
Edit 2 : updated my code here to reflect that i'd removed a shader in interfaceManager to actually get a square to draw at all : https://pastebin.com/pHHDsCvF for the shader code
Edit 3 : Ive determined it's something to do with my interface shaders, If i use PhongShader instead of InterfaceShader then it works exactly how I wanted it to
I can suggest you to modify the code this way:
WorldManager.renderAll(true); //true denotes yes to wireframe mode
glClear(GL_DEPTH_BUFFER_BIT);
InterfaceManager.renderAll();
This way you will clear depth buffer before rendering 2d interface.
The problem was that I was still applying transformations to the vertices after passing them to the shader.
By editing out the transformation (and later scrapping the entire vertex shader) in the InterfaceShader instance, the little squares were appearing in the right place
I have a tile engine using orthographic projection in immediate mode and I'm just trying to draw a 3d cube on top of my tile scene, in hopes that I can eventually incorporate 3d models into my engine instead of just sprites / textured quads. I would also like to make the tiles 3d for that slight bit of extra eye candy.. Hopefully I can eventually convert this to use modern OpenGL so I can take advantage of those extra features. Not on the top of my priority list at the moment. So on to the question.
I'm initializing OpenGL with this:
void initGL()
{
glDisable(GL_DEPTH_TEST);
glViewport( 0,0,SCREEN_WIDTH,SCREEN_HEIGHT);
//Initialize Projection Matrix
glMatrixMode( GL_PROJECTION );
glPushMatrix();
glLoadIdentity();
//Initialize Modelview Matrix
glMatrixMode( GL_MODELVIEW );
glPushMatrix();
glLoadIdentity();
glOrtho(0,SCREEN_WIDTH,SCREEN_HEIGHT,0,0,1);
glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_FASTEST);
//...setting some various other attributes, omitted for brevity...
glEnable(GL_TEXTURE_2D);
glClearColor( 0, 0, 0, 0 );
}
I have a function for drawing a cube that works.
void draw_cube()
{
/* position object */
glRotatef(30.0F, 1.0F, 0.0F, 0.0F);
glRotatef(30.0F, 0.0F, 1.0F, 0.0F);
/* draw six faces of a cube */
glBegin(GL_QUADS);
...vertices... (removed for brevity)
glEnd();
}
I made 2 functions for setting the 2d and 3d projection modes.
void set3d()
{
glEnable(GL_DEPTH_TEST);
glClear(GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glFrustum(0,SCREEN_WIDTH,0,SCREEN_HEIGHT, 0,1);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
void set2d()
{
glClear(GL_COLOR_BUFFER_BIT);
glDisable(GL_DEPTH_TEST);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0,SCREEN_WIDTH,SCREEN_HEIGHT,0,0,1);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
For the sake of completeness, some pseudocode of my textured quad drawing..
pushmatrix();
translate();
rotate();
-translate();
glbegin();
...vertices
glend();
popmatrix();
So far I have managed to get the cube to draw on top of the tiles, but it disappears after approximately 1 second to never be seen again until I run the program again.
Basically what I'm doing in the main loop is this:
move objects around, process collisions, etc.
set2d();
draw textured quads, lines, text, etc. in 2d mode.
set3d();
draw_cube();
My question is: Why is the cube disappearing, and are there any errors in my set2d() and set3d() functions?
You have quite a few problems in this code, too many to list in comments in fact.
Your projection matrices are changing the handedness of your post-projected coordinate space, which will affect polygon winding.
Stick to a single handedness, unless you want to reverse the direction used for front- / back-facing polygon facets (glFrontFace (...)) - it is CCW by default, but you will have to change it to CW when you use set3d (...) to maintain consistent behavior.
This problem arises because you have the Y-axis going different directions
The behavior your are describing, where the object appears briefly and then disappears is indicative of an issue with your matrix stack.
Are you calling initGL (...) more than once in your software? You will run into a stack overflow if you do this enough times since you needlessly push the current matrix onto the stack and never pop it off.
You cannot use 0.0 for zNear with a perspective projection matrix, this will result in wonky math during the perspective divide step that comes after transformation to clip-space; the depth buffer will not work correctly.
In fact, glFrustum (...) will generate a GL_INVALID_VALUE error and do exactly nothing if you pass a value ≤ 0.0 for zNear. On a related note, gluPerspective (...) will not do this since it is not actually part of OpenGL, but it is equally invalid behavior to pass such a value to gluPerspective (...).
I'm working on a little example, where I have loaded an object from a wavefront file - and am trying to get my picking right, I've gone over this and a few tutorials about 10 times... but must be missing something. Was wondering if anyone could provide an extra set of eyes.
I've used a saved list to draw the object, which appears fine on the screen... At the moment, when gl_select(x, y) runs, I get a hit no matter what, and if I enable the translate/rotate code (which is currently commented out) - I get no hits what-so-ever.
Relevant code blocks:
// gl_select, is called when the mouse is clicked, with its x and y coords
void gl_select(int x, int y)
{
GLuint buff[256];
GLint hits;
GLint view[4];
//Buffer to store selection data
glSelectBuffer(256, buff);
//Viewport information
glGetIntegerv(GL_VIEWPORT, view);
//Switch to select mode
glRenderMode(GL_SELECT);
//Clear the name stack!
glInitNames();
//Fill the stack with one element
glPushName(0);
//Restric viewing volume
glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();
//Restrict draw area
gluPickMatrix(x, y, 1.0, 1.0, view);
gluPerspective(60, 1, 0.0001, 1000.0);
//Draw the objects onto the screen
glMatrixMode(GL_MODELVIEW);
//Draw only the names in the stack
glutSwapBuffers();
DrawSavedObject();
//Back into projection mode to push the matrix
glMatrixMode(GL_PROJECTION);
glPopMatrix();
hits = glRenderMode(GL_RENDER);
cout << hits;
//Back to modelview mode
glMatrixMode(GL_MODELVIEW);
}
And the draw functions:
void DrawSavedObject()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glColor3f(1.0,0.0,0.0);
//translate and rotate
//glRotated(rotation,0.0,0.0,1.0);
//glTranslated(7.0, 7.0, 0.0);
//Draw the saved object
glLoadName(7);
glCallList(list_object);
glutSwapBuffers();
}
And where the list is saved:
void SaveDisplayList(){
glNewList(list_object, GL_COMPILE);
glVertexPointer(3, GL_DOUBLE, 3*sizeof(GLdouble), vertices);
glEnableClientState(GL_VERTEX_ARRAY);
glDrawElements(GL_TRIANGLES, verticesSize ,GL_UNSIGNED_INT, triangles);
glDisableClientState(GL_VERTEX_ARRAY);
glEndList();
}
Sorry again for the chunkiness of the code blocks.
A few things to consider here:
OpenGL selection mode is deprecated and never was HW accelerated, except on a few SGI boxes and 3DLabs GPUs.
DisplayLists don't mix with Vertex Arrays.
Why do you call glutSwapBuffers right before drawing your list of saved objects? Makes absolutely no sense at all.
I'm not sure if it's relevant but you're not supposed to store things like glVertexPointer in display lists. From the spec http://www.opengl.org/sdk/docs/man/xhtml/glNewList.xml:
Certain commands are not compiled into the display list but are
executed immediately, regardless of the display-list mode. These
commands are glAreTexturesResident, glColorPointer, glDeleteLists,
glDeleteTextures, glDisableClientState, glEdgeFlagPointer,
glEnableClientState, glFeedbackBuffer, glFinish, glFlush, glGenLists,
glGenTextures, glIndexPointer, glInterleavedArrays, glIsEnabled,
glIsList, glIsTexture, glNormalPointer, glPopClientAttrib,
glPixelStore, glPushClientAttrib, glReadPixels, glRenderMode,
glSelectBuffer, glTexCoordPointer, glVertexPointer, and all of the
glGet commands.
This could be what's causing your problem.
I know how to speed up rendering in 3d by simply rendering the nearest planes first.
But how do i get advantage of this type of method in 2d mode? I cant use depth testing because they are all in the same z-level.
So i was thinking if it could be speed up when i dont need to render the invisible parts of the layers "below". Is this possible?
Note that i am rendering in 3d mode, there may be 3d objects and 2d objects at the same time. So i cant switch to 2d render only, i always use 3d coordinates for everything. And i may rotate the camera as i wish, so camera-specific tricks arent acceptable.
Edit: i tried the method Ville suggested:
( http://img815.imageshack.us/img815/7857/zfighting.png )
but as you see, it will result in z-fighting.
The code i used for rendering that is here:
glDepthFunc(GL_LESS);
glEnable(GL_DEPTH_TEST);
glDisable(GL_TEXTURE_2D);
glDisable(GL_ALPHA_TEST);
glDisable(GL_POLYGON_OFFSET_FILL);
glColor4f(1,0,0,1);
DrawQuad(0, 0, 10, 10);
glColor4f(0,0,1,1);
DrawQuad(5, 5, 15, 15);
glDepthFunc(GL_LEQUAL);
It sounds like you are rendering all your "2D" objects on the same plane. You could render your 2D parts into an off-screen framebuffer with an orthographic projection and give them different Z values as datenwolf suggested. Then render the framebuffer texture into your main 3D scene.
What do you understand by 2D mode? Do you mean orthographic projection? Then I have good news: Depth testing works there perfectly as well. gluOrtho2D is basically the same like glOrtho(..., -1, 1); i.e. you have the Z range -1 ... 1 to spend.
EDIT due to comment:
It is perfectly possible to combine rendering several projections in one single frame:
void render_perspective_scene(void);
void render_ortho_scene(void);
void render_HUD();
void display()
{
float const aspect = (float)win_width/(float)win_height;
glViewport(0,0,win_width,win_height);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glFrustum(-aspect*near/lens, aspect*near/lens, -near/lens, near/lens, near, far);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
render_perspective_scene();
// just clear the depth buffer, so that everything that's
// drawn next will overlay the previously rendered scene.
glClear(GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-aspect*scale, aspect*scale, -scale, scale, 0, 1);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
render_ortho_scene();
// Same for the HUD, only that we render
// that one in pixel coordinates.
glClear(GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, win_width, 0, win_height, 0, 1);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
render_HUD();
}
Of course if you've fallen for those bad tutorials that place the projection matrix setup in the reshape handler you're of course mind blocked, to see that obvious solution.