Good morning,

I'm working through creating the spherical billboards technique outlined in this paper. I'm trying to create a shader that calculates the distance from the camera to all objects in the scene and stores the results in a texture. I keep getting either a completely black or white texture.

Here are my questions:

• I assume the position that's automatically sent to the vertex shader from ogre is in object space?
• The gpu interpolates the output position from the vertex shader when it sends it to the fragment shader. Does it do the same for my depth calculation or do I need to move that calculation to the fragment shader?
• Is there a way to debug shaders? I have no errors but I'm not sure I'm getting my parameters passed into the shaders correctly.

Here's my shader code:

void DepthVertexShader(
   float4 position : POSITION,
   uniform float4x4 worldViewProjMatrix,
   uniform float3 eyePosition,
   out float4 outPosition : POSITION,
   out float Depth
)
{
   // position is in object space
   // outPosition is in camera space
   outPosition = mul( worldViewProjMatrix, position );
   // calculate distance from camera to vertex
   Depth = length( eyePosition - position );
}

void DepthFragmentShader(
   float Depth : TEXCOORD0,
   uniform float fNear,
   uniform float fFar,
   out float4 outColor : COLOR
)
{
   // clamp output using clip planes
   float fColor = 1.0 - smoothstep( fNear, fFar, Depth );
   outColor = float4( fColor, fColor, fColor, 1.0 );
}

fNear is the near clip plane for the scene fFar is the far clip plane for the scene