Hi!
I've recently added normal mapping to my engine using vertex and pixel shaders in .vsh and .psh format. I thought I had got it all working perfectly as it ran without problem on my NVidia based desktop computer. However when I ran exactly the same code on my laptop with an ATI card it had a horrible graphics glitch. I tested the same code on multiple PC's any with NVidia cards ran the code without any problems, but any PC with an ATI card ran it with glitches.
I've loaded some screen shots from both which can be viewed at
http://downtoearthgames.co.uk/page_1199482304953.html
I was wondering if anyone else had ever come across this problem and managed to fix it?
The actual code for my shaders is shown below.
Vertex Shader:
float4x4 WorldViewProj; //our world view projection matrix
float4x4 WorldInverseTranspose; //our inverse transpose matrix
float4x4 World; //our world matrix
float4 lightPos; //our light position in object space
texture texture0; //our texture
texture texture1; //our normal map
float4 globalAmbient;
sampler2D texSampler0 : TEXUNIT0 = sampler_state
{
Texture = (texture0);
MIPFILTER = LINEAR;
MAGFILTER = LINEAR;
MINFILTER = LINEAR;
};
sampler2D texSampler1 : TEXUNIT1 = sampler_state
{
Texture = (texture1);
MIPFILTER = LINEAR;
MAGFILTER = LINEAR;
MINFILTER = LINEAR;
};
//application to vertex structure
struct a2v
{
float4 position : POSITION0;
float3 normal : NORMAL;
float2 tex0 : TEXCOORD0;
float3 tangent : TANGENT;
float3 binormal : BINORMAL;
};
//vertex to pixel shader structure
struct v2p
{
float4 position : POSITION0;
float2 tex0 : TEXCOORD0;
float2 tex1 : TEXCOORD1;
float3 lightVec : TEXCOORD2;
float att : TEXCOORD3;
float4 ambient :TEXCOORD4;
};
//pixel shader to screen
struct p2f
{
float4 color : COLOR0;
};
//VERTEX SHADER
void vs( in a2v IN, out v2p OUT )
{
//getting to position to object space
OUT.position = mul(IN.position, WorldViewProj);
//getting the position of the vertex in the world
float4 posWorld = mul(IN.position, World);
//getting vertex -> light vector
float3 light = normalize(lightPos - posWorld) ;
//calculating the binormal and setting the Tangent Binormal and Normal matrix
float3x3 TBNMatrix = float3x3(IN.tangent, IN.binormal , IN.normal);
//setting the lightVector
OUT.lightVec = mul(TBNMatrix, light) ;
//calculate the attenuation
OUT.att = 1/( 1 + ( 0 * distance(lightPos.xyz, posWorld) ) );
OUT.ambient = globalAmbient;
OUT.tex0 = IN.tex0;
OUT.tex1 = IN.tex0;
}
Pixel Shader:
texture texture0; //our texture
texture texture1; //our normal map
sampler2D texSampler0 : TEXUNIT0 = sampler_state
{
Texture = (texture0);
MIPFILTER = LINEAR;
MAGFILTER = LINEAR;
MINFILTER = LINEAR;
};
sampler2D texSampler1 : TEXUNIT1 = sampler_state
{
Texture = (texture1);
MIPFILTER = LINEAR;
MAGFILTER = LINEAR;
MINFILTER = LINEAR;
};
//vertex to pixel shader structure
struct v2p
{
float4 position : POSITION0;
float2 tex0 : TEXCOORD0;
float2 tex1 : TEXCOORD1;
float3 lightVec : TEXCOORD2;
float att : TEXCOORD3;
float4 ambient :TEXCOORD4;
};
//pixel shader to screen
struct p2f
{
float4 color : COLOR0;
};
//PIXEL SHADER
void ps( in v2p IN, out p2f OUT )
{
float4 globalAmbient = IN.ambient;
//calculate the color and the normal
float4 color = tex2D(texSampler0, IN.tex0);
/*this is how you uncompress a normal map*/
float3 normal = 2.0f * tex2D(texSampler1, IN.tex1).rgb - 1.0f;
//normalize the light
float3 light = normalize(IN.lightVec) ;
//set the output color
float diffuse = saturate(dot(normal, light)) + globalAmbient;
//multiply the attenuation with the color
OUT.color = IN.att * color * diffuse;
//OUT.color = float4 (normal,1.0);
//OUT.color = color * diffuse;
//OUT.color = color;
//OUT.color = float4(light,1.0);
//OUT.color = diffuse;
OUT.color.w = 1;
//OUT.color = globalAmbient;
}
I've tracked down where the problem is occuring to the line:
OUT.lightVec = mul(TBNMatrix, light) ;
the ATI cards seem unable to carry out this calculation, I've tried changing the way the TBNMatrix is calculated but to no avail, and am now at a loss. Any help would be much appreciated thanks!
