I am working on supporting older Radeon (8500 - 9200) and I have run into a problem when doing projective texturing. The problem is also that I don't own a card so testing is quite tedious.
I am doing texturing like this. First I am using this vertex program:
void main( float4 position : POSITION,
float3 normal : NORMAL,
float3 uv : TEXCOORD0,
float4 tangent : TEXCOORD1,
out float4 oPosition : POSITION,
out float4 oLightColor : COLOR,
out float3 oUv : TEXCOORD0,
out float4 oSpotlightUv : TEXCOORD1,
out float oRejectUv : TEXCOORD2,
uniform float4x4 worldViewProj,
uniform float4x4 spotViewProj,
uniform float3 LightPos,
uniform float4 LightColor,
uniform float3 LightDirMul)
{
oPosition = mul(worldViewProj, position);
oUv = uv;
oSpotlightUv = mul(spotViewProj,position);
oRejectUv.x = oSpotlightUv.z + 0.5;
oLightColor = LightColor;
}
and I am using a modulative texture enviroment (no fragment shader used).
This is how it looks on my comp (GF 6800GT):
and here is how it looks on a Radeon 9200
The thing is that this works on Geforce 4Ti and if I change the vertex program to:
out float3 oSpotlightUv : TEXCOORD1,
[...]
oUv = uv;
oSpotlightUv = uv;
It all works as predicted, ie the normal texture get modulated with the spotlight but without any projection.
My idea is that the Radeon for some reason does not divide the x,y and z coords of oSpotlightUv before getting the color from the projective texture. But I have no idea why that is so. It seems like I reproduce the error on my own card if I write:
out float3 oSpotlightUv : TEXCOORD1,
I am in bad need of help with this.
Thanks in advance!
