I have some transparent decals rendered into a separate framebuffer. Now I'm trying to blend this buffer with the back buffer (active target).
I'm assuming that I have to load the color buffer of the fbo as a texture in a fragment shader and output the texture color to the active target. How can I tell the graphics card to do this operation for every pixel?
Draw a quad or two triangles that cover the whole screen.
my code for the fullscreen rectangle/quad
this is old method - from OpenGL 1.1, but works :) For new OpenGL 3.* you have to use VBO/Arrays
glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
glLoadIdentity();
glBegin(GL_QUADS);
glTexCoord2f( 0,0 );
glVertex3d( -1.0,-1.0, 0 );
glTexCoord2f( 1,0 );
glVertex3d( 1.0,-1.0, 0 );
glTexCoord2f( 1,1 );
glVertex3d( 1.0, 1.0, 0 );
glTexCoord2f( 0,1 );
glVertex3d( -1.0, 1.0, 0 );
glEnd();
glMatrixMode(GL_PROJECTION);
glPopMatrix();
glMatrixMode(GL_MODELVIEW);
glPopMatrix();
of course you have to setup textures before
Related
I'm trying to show a texture in Qt with opengl but it just doesn't show the texture when i run.
I did some research and found out I needed to make the height and width of the texture as a power of 2. my texture is now (1024x1024).
I also added a lot of glTexParameterf's that could resolve my problem, but still no luck.
void WorldView::paintGL ()
{
this->dayOfYear = (this->dayOfYear+1);
this->hourOfDay = (this->hourOfDay+1) % 24;
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
// store current matrix
glMatrixMode( GL_MODELVIEW );
glPushMatrix( );
gluLookAt(camPosx ,camPosy ,camPosz,
camViewx,camViewy,camViewz,
camUpx, camUpy, camUpz );
//Draw Axes
glDisable( GL_LIGHTING );
glBegin(GL_LINES);
glColor3f(1.0, 0.0, 0.0);
glVertex3f(0.0, 0.0, 0.0);
glVertex3f(10.0, 0.0, 0.0);
glColor3f(0.0, 1.0, 0.0);
glVertex3f(0.0, 0.0, 0.0);
glVertex3f(0.0, 10.0, 0.0);
glColor3f(0.0, 0.0, 1.0);
glVertex3f(0.0, 0.0, 0.0);
glVertex3f(0.0, 0.0, 10.0);
glEnd();
//load texture
QImage img;
if(!img.load(":/files/FloorsCheckerboardSmall.bmp"))
printf("could not open image");
//try showing texture
glEnable( GL_LIGHTING );
glEnable( GL_COLOR_MATERIAL );
glEnable(GL_TEXTURE_2D);
unsigned int m_textureID;
glGenTextures(1, &m_textureID);
glBindTexture(GL_TEXTURE_2D,m_textureID);
glTexImage2D(GL_TEXTURE_2D,0,(GLint)img.depth(),(GLsizei)img.width(),(GLsizei)img.height(),0,GL_RGB,GL_UNSIGNED_BYTE,img.bits());
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_REPEAT);
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T,GL_REPEAT);
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
glTexEnvf(GL_TEXTURE_ENV,GL_TEXTURE_ENV_MODE,GL_MODULATE);
glColor3d(1.0,0.0,0.0);
glBegin(GL_POLYGON);
glTexCoord2d(0.0,5.0);
glVertex2d(0.0,3.0);
glTexCoord2d(0.0,0.0);
glVertex2d(0.0,0.0);
glTexCoord2d(5.0,0.0);
glVertex2d(3.0,0.0);
glTexCoord2d(5.0,5.0);
glVertex2d(3.0,3.0);
glEnd();
}
EDIT1: Could it be my texture is too big?
EDIT2: glBindTexture(GL_TEXTURE_2D,m_textureID); placed before glBindTexture instead of before glColor3d
SOLVED: My img.depth() returned an invalid internalFormat value. I replaced this GLint with the valid interalFormat value GL_RGBA. I also changed the format from GL_RGB to GL_RGBA (see genpfaults answer)
glTexImage2D(GL_TEXTURE_2D,0,GL_RGBA,(GLsizei)img.width(),(GLsizei)img.height(),0,GL_RGBA,GL_UNSIGNED_BYTE,img.bits());
You have to call
glBindTexture(GL_TEXTURE_2D,m_textureID);
before calling glTexImage2D(...). Or OpenGL won't know where the data you send it belongs.
vvvvvvvvvvvvvvvvvv
glTexImage2D(GL_TEXTURE_2D,0,(GLint)img.depth(),(GLsizei)img.width(),(GLsizei)img.height(),0,GL_RGB,GL_UNSIGNED_BYTE,img.bits());
img.depth() returns 32
Then you need to pass in a valid internalFormat value, not img.depth(). Try GL_RGBA.
You should also set format to GL_RGBA since img.bits() is actually four-component.
I have programmed a little raytracer in c++,
and want to show the raytraced image in a window.
I tried using a pixel buffer object in opengl,
then map the buffer into memory and manipulate the pixels one by one,
but at fullscreen resolution 1920x1080, I only get 4 fps
without raytracing and without changing the pixels colors
just the mapping and unmapping!
so i'm basically looking for the fastest way to display a raytraced image in a window.
i'm currently doing this way:
glBindBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB, pbo);
glBufferDataARB(GL_PIXEL_UNPACK_BUFFER_ARB, width * height * 4, 0, GL_STREAM_DRAW_ARB);
if (pixels = (uint*)glMapBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB, GL_WRITE_ONLY_ARB))
{
//modify pixels
glUnmapBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB);
}
else
return;
//copy from pbo to texture
glBindTexture(GL_TEXTURE_2D, pbo_texture);
glBindBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB, pbo);
glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, width, height, GL_BGRA, GL_UNSIGNED_BYTE, 0);
glEnable(GL_TEXTURE_2D);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
//draw image
glColor4f(1.0, 1.0, 1.0, 1.0);
glBindTexture(GL_TEXTURE_2D, pbo_texture);
glBegin(GL_QUADS);
glTexCoord2f(0.0, 1.0); glVertex3f(-1.0, -1.0, 0.0);
glTexCoord2f(1.0, 1.0); glVertex3f( 1.0, -1.0, 0.0);
glTexCoord2f(1.0, 0.0); glVertex3f( 1.0, 1.0, 0.0);
glTexCoord2f(0.0, 0.0); glVertex3f(-1.0, 1.0, 0.0);
glEnd();
glutSwapBuffers();
glBindBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB, 0);
glBindTexture(GL_TEXTURE_2D, 0);
Check the memory traversal if you use loops. You should traverse your buffer in the right order, otherwise you may have cache miss at each iteration. If you use nested loops sometimes you only have to switch the x/y iteration order.
Also, don't read data from graphic memory. It tends to be slow. Only write to PBO.
It looks like a syncro issue. I'm not sure you need to map pbo at every frame. Check this link on OpenGL Pixel Buffer Object (PBO). There's also a workaround for stalls which could improve things
I've managed to successfully use OpenGL's stencil buffer for a single instance in a scene. However, I'm unsure of how to use it in two different places in the same scene. Defining two stencil shapes in sequence prevents either from working, and my attempts to nest one use inside of the other didn't work either. I've seen examples of multiple uses of stencil buffer in the same scene, but I was not able to understand or adapt the code. Here is what I've been able to get working so far.
void display(void) {
// store floor shape in stencil buffer
glClearStencil(0);
glClear(GL_STENCIL_BUFFER_BIT);
glEnable(GL_STENCIL_TEST);
glStencilMask(1);
glStencilFunc(GL_ALWAYS, 1, 1);
glStencilOp(GL_REPLACE, GL_REPLACE, GL_REPLACE);
floor->draw();
glBegin(GL_QUADS); //
glVertex3f(0.0, 0.0, 0.0); //
glVertex3f(0.0, 100.0, 0.0); //
glVertex3f(0.0, 100.0, 100.0); //
glVertex3f(0.0, 0.0, 100.0); //
glEnd(); //
// draw scene outside floor
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
scene();
// draw reflection of scene in floor
glStencilFunc(GL_EQUAL, 1, 1);
glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
glPushMatrix();
glScalef(1.0, 1.0, -1.0);
scene();
glPopMatrix();
glDisable(GL_STENCIL_TEST);
// draw translucent floor
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glColor4f(1.0, 1.0, 1.0, 0.7);
floor->draw();
//windowHole();
glDisable(GL_BLEND);
glFlush();
glutSwapBuffers();
glutPostRedisplay();
}
I'm trying to create a mirror in OpenGL. Most references I've found recommend using the stencil buffer to define the boundaries of the mirror itself and using a combination of translation and scaling matrices for the actual reflection. I managed to get this to work when the scene is viewed so that no objects are in front of the mirror. However, when an object is in front of the mirror the overlapping part is not shown, making it look as if it's behind the mirror. There's a good chance that I'm misunderstanding how the stencil buffer works, as this is the first time I've tried using it, but I could also be making some mistake regarding depth or something else. I'd appreciate any suggestions. Here is the code.
#include <gl/glut.h>
// perspective
void view(void) {
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-2.0, 2.0, -2.0, 2.0, -2.0, 2.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glRotatef(-85.0, 1.0, 0.0, 0.0);
glScalef(0.25, 0.25, 0.25);
}
void init(void) {
glEnable(GL_DEPTH_TEST);
glClearStencil(0);
glEnable(GL_STENCIL_TEST);
}
void mirror(GLboolean inside, GLfloat vertSet[4][3]) {
GLint i;
if(inside)
glBegin(GL_QUADS); // draw inside of mirror
else
glBegin(GL_LINE_LOOP); // draw frame of mirror
for(i = 0; i < 4; i++)
glVertex3fv(vertSet[i]);
glEnd();
}
void scene(void) {
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
glRotatef(90.0, 1.0, 0.0, 0.0);
glutSolidTeapot(1.0);
glPopMatrix();
}
void display(void) {
GLfloat vertSet1[4][3] = {{-3.0, 3.0, 0.0}, {2.0, 3.0, 0.0},
{2.0, 3.0, 2.0}, {-3.0, 3.0, 2.0}};
view();
// store mirror shape in the stencil buffer.
glClear(GL_STENCIL_BUFFER_BIT);
glStencilFunc(GL_ALWAYS, 1, 1);
glStencilOp(GL_REPLACE, GL_REPLACE, GL_REPLACE);
mirror(true, vertSet1);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// draw mirror frame.
glColor3f(0.0, 0.0, 0.0);
mirror(false, vertSet1);
// draw scene outside mirror
glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
glStencilFunc(GL_NOTEQUAL, 1, 1);
scene();
// draw reflection of scene in mirror
glStencilFunc(GL_EQUAL, 1, 1);
glTranslatef(0.0, 3.0, 0.0);
glScalef(1.0, -1.0, 1.0);
glTranslatef(0.0, -3.0, 0.0);
scene();
glFlush();
glutSwapBuffers();
glutPostRedisplay();
}
int main (int argc, char **argv) {
glutInit(&argc, argv);
glutInitWindowSize(500, 500);
glutInitWindowPosition(0, 0);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_STENCIL | GLUT_DEPTH);
glutCreateWindow("");
glClearColor(1.0, 1.0, 1.0, 0.0);
init();
glutDisplayFunc(display);
glutMainLoop();
}
The idea of the stencil is, that you draw it when you'd normally render the mirror's glass within the scene. You want the drawing of the stencil to be depth tested. When you finished rendering your scene, you add a clip plane in the plane of the mirror, then you clear the depth buffer and redraw the scene. Since you clear the depth buffer you need the stencil to be depth tested first to make the mirror not overdraw already drawn objects in the world.
Note that drawing a mirror is essentially the same as drawing a portal.
This is my code for doing reflection in old opengl, hope this helps
Please note that most of the code comes from NeHe tutorial: http://nehe.gamedev.net/tutorial/clipping__reflections_using_the_stencil_buffer/17004/
double eqr[] = { 0.0f, -1.0f, 0.0f, 0.0f };
glColorMask(0, 0, 0, 0);
glEnable(GL_STENCIL_TEST);
glStencilFunc(GL_ALWAYS, 1, 1);
glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
glDisable(GL_DEPTH_TEST);
DrawFloor(); // draw flor to the stencil buffer
glColorMask(1, 1, 1, 1);
glStencilFunc(GL_EQUAL, 1, 1);
glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
glEnable(GL_CLIP_PLANE0);
glClipPlane(GL_CLIP_PLANE0, eqr);
glPushMatrix();
glScalef(1.0f, -1.0f, 1.0f);
//glLightfv(GL_LIGHT0, GL_POSITION, light_pos);
glFrontFace(GL_CW);
glTranslatef(0.0f, 0.3f, 0.0);
RenderScene();
glFrontFace(GL_CCW);
glPopMatrix();
glDisable(GL_CLIP_PLANE0);
glDisable(GL_STENCIL_TEST);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glColor4f(0.6f, 0.7f, 1.0f, 0.5f);
DrawFloor(); // draw floor second time
glDisable(GL_BLEND);
// draw normal scene
glPushMatrix();
glColor3f(1.0f, 1.0f, 1.0f);
glTranslatef(0.0f, 0.3f, 0.0);
RenderScene();
glPopMatrix();
For better result you might use RenderToTexture or use cube maps
I want to draw a logo(3D awards) at the corner of the window(fixed position when change camera)
here is my code for drawing fullscreen rectangle (in old opengl)
glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
glLoadIdentity();
glBegin(GL_QUADS);
glTexCoord2f( 0,0 );
glVertex3d( -1.0,-1.0, 0 );
glTexCoord2f( 1,0 );
glVertex3d( 1.0,-1.0, 0 );
glTexCoord2f( 1,1 );
glVertex3d( 1.0, 1.0, 0 );
glTexCoord2f( 0,1 );
glVertex3d( -1.0, 1.0, 0 );
glEnd();
glMatrixMode(GL_PROJECTION);
glPopMatrix();
glMatrixMode(GL_MODELVIEW);
glPopMatrix();
just disable depth buffer abd set the texture to be able to draw your logo in front of eferything
Of course you can change the position and the size of it
Could do it like so:
Draw your scene
Disable the depth test (or clear the depth buffer if you need self-depth testing to draw the model correctly)
Set a new matrix on the stack which ignores camera position.
Draw the logo.