Jump to content
  • Advertisement
Sign in to follow this  

Transforms in vertex program?

This topic is 3684 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

I am currently using the vertex program from the Cg Toolkit:
struct vertex_input
  float4 position : POSITION;
  float4 normal   : NORMAL;

struct vertex_output
  float4 position : POSITION;
  float4 color    : COLOR;

vertex_output main(
                     vertex_input IN
                   , uniform float4x4 ModelViewProj 
                   , uniform float4x4 ModelViewIT   
                   , uniform float4   light_vector	
  vertex_output OUT;  
  // Transform vertex position into homogenous clip-space.
  OUT.position = mul(ModelViewProj, IN.position);  
  // Transform normal from model-space to view-space/eye-space
  float3 normalVec = normalize(mul(ModelViewIT, IN.normal).xyz);
  // Store normalized light vector.
  float3 lightVec  = normalize(light_vector.xyz);
  // Calculate half angle vector.
  float3 eyeVec    = float3(0.0, 0.0, 1.0);  
  //float3 halfVec   = normalize(lightVec);
  float3 halfVec   = normalize(lightVec + eyeVec);
  // Calculate diffuse component.
  float diffuse    = dot(normalVec, lightVec);
  // Calculate specular component.
  float specular   = dot(normalVec, halfVec);
  // Use the lit function to compute lighting vector from
  // diffuse and specular values.
  float4 lighting  = lit(diffuse, specular, 32);
  // Blue diffuse material
  float3 diffuseMaterial = float3(0.0, 0.0, 1.0);
  // White specular material
  float3 specularMaterial = float3(1.0, 1.0, 1.0);
  // Combine diffuse and specular contributions and
  // output final vertex color.
  OUT.color.rgb = lighting.y * diffuseMaterial + lighting.z * specularMaterial;
  OUT.color.a = 1.0;
  return OUT;  

In the Cg tutorial the chain of spaces are defined in the following way: Object/modelSpc -> WorldSpc -> Eye/ViewSpc -> ClipSpc -> WindowSpc. But in the second statement in the above vertexprogram the normal is transformed into EyeSpc using the "inverse" modelView matrix ModelViewIT. But does ModelViewIT not transform FROM EyeSpc TO ObjectSpc and not the other way around??

Share this post

Link to post
Share on other sites
Sign in to follow this  

  • Advertisement

Important Information

By using GameDev.net, you agree to our community Guidelines, Terms of Use, and Privacy Policy.

GameDev.net is your game development community. Create an account for your GameDev Portfolio and participate in the largest developer community in the games industry.

Sign me up!