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ErikPeeters

Selective GL_DEPTH_TEST question

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Hi all, I have a depth buffer question: In my code I render the follwing list:
m_List = glGenLists(1);
glNewList(m_List, GL_COMPILE);

    glPushMatrix();

    glDisable(GL_DEPTH_TEST);

    glBindTexture(GL_TEXTURE_2D, m_unTextures[9]);
    glEnable(GL_TEXTURE_2D);
			
    glEnable(GL_BLEND);
    glBlendFunc(GL_DST_COLOR, GL_ONE_MINUS_SRC_COLOR);

    glCallList(List2);

    glBlendFunc(GL_SRC_COLOR, GL_ONE_MINUS_SRC_COLOR);
    glBindTexture(GL_TEXTURE_2D, m_unTextures[10]);

    glCallList(List3);

    glEnable(GL_DEPTH_TEST);
    
    glDisable(GL_BLEND);
    glDisable(GL_TEXTURE_2D);

    glPopMatrix();
  
endlist()

The code masks a part of the texture and shows another part. And becasue of the disabling of the depth test all sides of the textured lists are viewable. But because of the disabling of the depth test when I render a textured quad ontop of the m_list list it blends with the texture of the quad. My question is: is there a way that I can use the disabling of the depth test for m_List but when I place an object over m_List it is rendered behind the object?

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You have to draw your "normal" geometry first. Then sort all faces you want to draw that way back to front, disable the depth mask ( glDepthMask(GL_FALSE) ) and render the sortet faces. So you get the effect you want.

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Thanks for the reply, Ingrader.

So, if I nderstand correctly I have to do the following pseudo-code:


void RenderScene()
{
// Draw all objects that do have or require depth test.
DrawAllNormalObjects();

// Sort all objects that do require dept test
// from back to front.
SortAllOtherObjects();

glDepthMask(GL_FALSE);

// Render the sorted faces with depth test disabled
DrawAllOtherObjects();
}




Do I need to enable the depth mask again at any time?

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Yes, after you've done drawing the other objects you have to enable the depth mask again. Depth testing stays enabeled.

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