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Editorial Team
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Asked: 2026-06-08T18:23:28+00:00

I’ve got a problem with my render to texture process. When I render the

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I’ve got a problem with my render to texture process. When I render the scene with width = height = 512 it has nearly no errors but the smaller the texture and scene gets, the more errors it gets.
The error is that regions of the texture are black, what makes no sense.

Here are some screenshots

512*512: http://www.ld-host.de/uploads/images/d9452fa0ba28494830fd96f0f15b9eba.png
128*128: http://www.ld-host.de/uploads/images/a39c141282a622f086d4a96b070a56a3.png

Here is my code how I render to texture and use the texture later

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
    glMatrixMode(GL_MODELVIEW)
    glLoadIdentity()
    gluLookAt(0,0,200,0,0,-1,0,1,0)


    self.fbos = glGenFramebuffersEXT(1)
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, self.fbos)
    self.depthbuffers = (glGenRenderbuffersEXT(1)
    glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, self.depthbuffers)
    glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT, width, height)
    glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, GL_RENDERBUFFER_EXT, self.depthbuffers)       

    self.textures = glGenTextures(1)
    glBindTexture(GL_TEXTURE_2D, self.textures)
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER, GL_LINEAR)
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER, GL_LINEAR)
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8,  width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, None);
    glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT,  GL_TEXTURE_2D, self.textures, 0);
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, self.fbos);

    glEnable(GL_CLIP_PLANE0)
    glEnable(GL_CLIP_PLANE1)
    glClipPlane(GL_CLIP_PLANE0, (0,0,1,-1 * self.start + self.diff))       
    glClipPlane(GL_CLIP_PLANE1, (0,0,-1,self.start))   

    # render the mesh
    glTranslatef(-64,-64,-64)
    glEnableClientState(GL_VERTEX_ARRAY) # Enable something in OpenGL 
    glEnableClientState(GL_COLOR_ARRAY) # Enable something in OpenGL
    glBindBuffer(GL_ARRAY_BUFFER,self.vbo[1]) 
    glColorPointer(3,GL_FLOAT,0,None) # Tell OpenGL that it contains only ColorValues
    #Now the vertex Buffer with positions
    glBindBuffer(GL_ARRAY_BUFFER,self.vbo[0]) 
    glVertexPointer(3,GL_FLOAT,0,None) # Tell OpenGL that it contains the Positions for each Points
    glDrawArrays(GL_TRIANGLES,0,len(self.verts)+len(self.color))    # Merge both

    glDisableClientState(GL_COLOR_ARRAY); 
    glDisableClientState(GL_VERTEX_ARRAY);
    glDisable(GL_CLIP_PLANE0)
    glDisable(GL_CLIP_PLANE1)
    glBindTexture(GL_TEXTURE_2D,0)
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0); 

    #Plane for showing texture
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
    glMatrixMode(GL_MODELVIEW)
    glLoadIdentity()
    gluLookAt(0,0,1,0,0,0,0,1,0)
    glClearColor(1,1,1,0)

    glEnable(GL_TEXTURE_2D)

    glBindTexture(GL_TEXTURE_2D, self.textures)
    glBegin(GL_QUADS)
    glNormal3f(0.0, 1.0, 0.0)
    glTexCoord2f(0.0, 0.0)
    glVertex3f(-1, 1, -1)
    glTexCoord2f(1.0, 0.0)
    glVertex3f(1, 1, -1)
    glTexCoord2f(1.0, 1.0)
    glVertex3f(1, -1, -1)
    glTexCoord2f(0.0, 1.0)
    glVertex3f(-1, -1, -1)
    glEnd();
    glDisable(GL_TEXTURE_2D)

    pygame.display.flip()

How can I achieve a better quality for the smaller texture? The mesh has no holes but the texture sometimes has.

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1 Answer

  1. Editorial Team

    I don’t know what exactly you’re expecting to see. You’re drawing triangles/cubes/etc that are clearly smaller than the size of a pixel/sample size. Therefore, not all of them are going to be visible.

    This is a standard aliasing problem: triangles that don’t cover the center of a pixel/sample will not be visible. That’s the nature of rasterization. And the only way to fix aliasing is to increase the number of samples you use. You can render at a higher resolution and downscale, or you could use MSAA or another real aliasing technique.

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