GPU support for Vertex Texture Fetch (VTF)

Sathish,

   The PowerVR documentation does not state specifically that VTF is or is not supported.  However, I did find this one example vertex shader in the SDK that uses a sampler2D which suggests that it should work.  There is an article here that explains how to test that VTF is supported.  I recommend that they try this for themselves.

http://www.opengl.org/wiki/Vertex_Texture_Fetch

This example vertex shader is from the PowerVR Graphics SDK at  TrainingCourse\28_DisplacementMap\OGLES2\VertShader.vsh

attribute highp   vec3  inVertex;
attribute mediump vec3  inNormal;
attribute mediump vec2  inTexCoord;

uniform highp   mat4  MVPMatrix;
uniform mediump vec3  LightDirection;
uniform mediump    float  DisplacementFactor;

varying lowp    float  LightIntensity;
varying mediump vec2   TexCoord;

uniform sampler2D  sDisMap;

void main()
{
    /*
        Calculate the displacemnt value by taking the colour value from our texture
        and scale it by out displacement factor.
    */
    mediump float disp = texture2D(sDisMap, inTexCoord).r * DisplacementFactor;

    /*
        Transform position by the model-view-projection matrix but first
        move the untransformed position along the normal by our displacement
        value.
    */
    gl_Position = MVPMatrix * vec4(inVertex + (inNormal * disp), 1.0);

    // Pass through texcoords
    TexCoord = inTexCoord;
   
    // Simple diffuse lighting in model space
    LightIntensity = dot(inNormal, -LightDirection);
}

Regarding memory bandwidth considerations, I recommend this article that is in the PowerVR SDK as well:

POWERVR SGX.OpenGL ES 2.0 Application Development Recommendations.1.8f.External.pdf

Regards, Clay