How to perform depth test in pixel shader
September 10, 2009 02:09 AM
Hi Guys,
I wanted to know how we can perform depth test in
pixel shader for knowledge purpose.I am using openGL ES 2.0 and
GLSL 1.0.I have tried to search on google also but i didnt get any much
info on this topic.Please give me some link or if any document is there.
Regards,
Parmar.
813
September 10, 2009 08:08 AM
Doing depth testing yourself would require reading what is already in the depth buffer and reading the depth buffer is not possible from a pixel shader.
Sig: http://glhlib.sourceforge.net
an open source GLU replacement library. Much more modern than GLU.
float matrix[16], inverse_matrix[16];
glhLoadIdentityf2(matrix);
glhTranslatef2(matrix, 0.0, 0.0, 5.0);
glhRotateAboutXf2(matrix, angleInRadians);
glhScalef2(matrix, 1.0, 1.0, -1.0);
glhQuickInvertMatrixf2(matrix, inverse_matrix);
glUniformMatrix4fv(uniformLocation1, 1, FALSE, matrix);
glUniformMatrix4fv(uniformLocation2, 1, FALSE, inverse_matrix);
an open source GLU replacement library. Much more modern than GLU.
float matrix[16], inverse_matrix[16];
glhLoadIdentityf2(matrix);
glhTranslatef2(matrix, 0.0, 0.0, 5.0);
glhRotateAboutXf2(matrix, angleInRadians);
glhScalef2(matrix, 1.0, 1.0, -1.0);
glhQuickInvertMatrixf2(matrix, inverse_matrix);
glUniformMatrix4fv(uniformLocation1, 1, FALSE, matrix);
glUniformMatrix4fv(uniformLocation2, 1, FALSE, inverse_matrix);
2,682
September 10, 2009 09:22 AM
Don't think you can, pixels don't get to the pixel shader if they fail the depth test.
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September 10, 2009 09:29 AM
Thanks V-man for your reply.As usual you replied for my question.
I think i could not formed the proper sentence.
How i will get the depth value of a pixel in
fragment shader.And can we write our own implementation
for depth test in vertex shader.
Regards,
Parmar.
I think i could not formed the proper sentence.
How i will get the depth value of a pixel in
fragment shader.And can we write our own implementation
for depth test in vertex shader.
Regards,
Parmar.
813
September 10, 2009 11:30 AM
Quote: Original post by Nanoha
Don't think you can, pixels don't get to the pixel shader if they fail the depth test.
Wrong. If you output your own depth value, the depth test happens after the pixel shader stage. Read about gl_FragDepth.
Quote: Original post by parmar
How i will get the depth value of a pixel in
fragment shader.And can we write our own implementation
for depth test in vertex shader.
You could do render to a depth texture in pass 1, then in the next pass, read that texture and do your own depth testing. Normally, you do this in a pixel shader.
Sig: http://glhlib.sourceforge.net
an open source GLU replacement library. Much more modern than GLU.
float matrix[16], inverse_matrix[16];
glhLoadIdentityf2(matrix);
glhTranslatef2(matrix, 0.0, 0.0, 5.0);
glhRotateAboutXf2(matrix, angleInRadians);
glhScalef2(matrix, 1.0, 1.0, -1.0);
glhQuickInvertMatrixf2(matrix, inverse_matrix);
glUniformMatrix4fv(uniformLocation1, 1, FALSE, matrix);
glUniformMatrix4fv(uniformLocation2, 1, FALSE, inverse_matrix);
an open source GLU replacement library. Much more modern than GLU.
float matrix[16], inverse_matrix[16];
glhLoadIdentityf2(matrix);
glhTranslatef2(matrix, 0.0, 0.0, 5.0);
glhRotateAboutXf2(matrix, angleInRadians);
glhScalef2(matrix, 1.0, 1.0, -1.0);
glhQuickInvertMatrixf2(matrix, inverse_matrix);
glUniformMatrix4fv(uniformLocation1, 1, FALSE, matrix);
glUniformMatrix4fv(uniformLocation2, 1, FALSE, inverse_matrix);
September 10, 2009 01:14 PM
Thanks V-man,
@V-man Is any document or sample is there for this concept.
so I can go through it.I am a regular reader of this
community but i didnt get much info on this concept.
@Nanoha thanks for your reply.
813
September 10, 2009 05:30 PM
There is this extension
examples are on that page
http://www.opengl.org/wiki/GL_EXT_framebuffer_object
There is the GL 3.0 version
http://www.opengl.org/wiki/Framebuffer_Objects
examples are on that page
http://www.opengl.org/wiki/GL_EXT_framebuffer_object
There is the GL 3.0 version
http://www.opengl.org/wiki/Framebuffer_Objects
Sig: http://glhlib.sourceforge.net
an open source GLU replacement library. Much more modern than GLU.
float matrix[16], inverse_matrix[16];
glhLoadIdentityf2(matrix);
glhTranslatef2(matrix, 0.0, 0.0, 5.0);
glhRotateAboutXf2(matrix, angleInRadians);
glhScalef2(matrix, 1.0, 1.0, -1.0);
glhQuickInvertMatrixf2(matrix, inverse_matrix);
glUniformMatrix4fv(uniformLocation1, 1, FALSE, matrix);
glUniformMatrix4fv(uniformLocation2, 1, FALSE, inverse_matrix);
an open source GLU replacement library. Much more modern than GLU.
float matrix[16], inverse_matrix[16];
glhLoadIdentityf2(matrix);
glhTranslatef2(matrix, 0.0, 0.0, 5.0);
glhRotateAboutXf2(matrix, angleInRadians);
glhScalef2(matrix, 1.0, 1.0, -1.0);
glhQuickInvertMatrixf2(matrix, inverse_matrix);
glUniformMatrix4fv(uniformLocation1, 1, FALSE, matrix);
glUniformMatrix4fv(uniformLocation2, 1, FALSE, inverse_matrix);
September 11, 2009 12:55 AM
I have a one doubt about depth test.
After vertex sahder traingle will rasterize,and it will get color and
depth value of per fragemnt.So why we dont have the depth test there only.
Even some fargment is occuleded we are accesing the per fragemnt color
and texture fetch in pixel shader.Can any one suggest.
Parmar.
2,625
September 11, 2009 01:06 AM
Search for early Z pass, pre z pass, etc. you generally turn off color writes, and only write depth, so you dont bother with textures in an early z pass, so there is no color value being written.
2,990
September 11, 2009 01:37 AM
Couldn't this depth test (the rendered to texture thing) used to draw decals on surfaces?
simply:
if(fabs(frag_depth-texture_depth(x,y))> tolerance )
discard fragment
No need of clipping, just draw it
simply:
if(fabs(frag_depth-texture_depth(x,y))> tolerance )
discard fragment
No need of clipping, just draw it
This topic is closed to new replies.
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