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empirical2

GLSL Referencing a texture unit by variable

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empirical2    567
Basically before I abandon this I just want to check if what I am doing is even possible. I have tried googling but guess im not using the right keywords.

This is my shader

[source]$VERTEX

varying vec2 vTexCoord;
varying vec4 vColor;
varying vec3 vertex_light_position;
varying vec3 vertex_normal;

void main(void)
{
vertex_normal = normalize(gl_NormalMatrix * gl_Normal);
vertex_light_position = normalize(gl_LightSource[0].position.xyz);
vTexCoord = gl_MultiTexCoord0;
vColor=gl_Color;
gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;

}



$FRAGMENT

uniform sampler2D Texture[8];

varying vec2 vTexCoord;
varying vec4 vColor;
varying vec3 vertex_light_position;
varying vec3 vertex_normal;

void main (void)
{
int i1=int(vColor.r*10);
int i2=int(vColor.g*10);

vec4 c1= texture2D(Texture[i1], vTexCoord).rgba;
vec4 c2= texture2D(Texture[i2], vTexCoord).rgba;

float diffuse_value = max(dot(vertex_normal, vertex_light_position), 0.0)*1.3;
gl_FragColor=((c1*vColor.b)+(c2*(1.0-vColor.b)))*(diffuse_value+0.3);
gl_FragColor.a=1.0;
} [/source]

What am I trying to do?

Each triangle in the VBO is a blend of two textures. But the two textures vary with each triangle. I am trying to specify which two textures to use in the R & G color components. With conditional branching instead it works as I want, but I wanted to make it more efficient and scale-able for the future.

When I try to use the above code it compiles OK, but fails to link. I am unable to retrieve a link log.
However, if I use constants (e.g i1=0; i2=1) it compiles and links. I assume because all that is optimized away.

Im new to shaders so Im hoping someone will cast an eye over and say either "You cant do that" in which case I can switch to branching or look further into texture arrays, or "you can do that" in which case Ill plod on with it.

Cheers.

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