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cohr

OpenGL depth and Cg shaders

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I am writing a Ray tracer in Cg shading language, and want to calculate the depth to the nearest object in the fragment shader. The ray tracer works much like a skybox, where each side in the skybox is raytraced. Adding depth to the output enables me to add other objects (non raytraced) to the sceene. How do I calculate the depth to coorespond with the depth in the openGL depth buffer? For reference: Raytraced only. A sceene with no aditional non raytraced objects. With non-raytraced object. The white box (non raytraced) is added. But since the depth information is wayback the sphere is not excluding most of the white box.

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Problem solved:

found the solution here:
http://www.gpgpu.org/forums/viewtopic.php?p=14124

float zFar = 400;
float zNear = 0.1;

float z = length(ray.position-IN.Eye);
float a = zFar / ( zFar - zNear );
float b = zFar * zNear / ( zNear - zFar );
float depth = ( a + b / z );

Turned out to be quiet a simple solution.

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