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OpenGL Cg fragment program arrays

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Gumgo    968
I'm having some trouble getting the following Cg fragment program to compile:
struct Input {
	float3 position		: TEXCOORD0;
	float3 normal		: TEXCOORD1;
	float2 texCoord		: TEXCOORD2;
	float3 tangent		: TEXCOORD3;
	float3 binormal		: TEXCOORD4;

// textures
uniform sampler2D diffuseMap		: TEXUNIT0;
uniform sampler2D specularMap		: TEXUNIT1;
uniform sampler2D bumpMap			: TEXUNIT2;
uniform sampler2D reflectMap		: TEXUNIT3;
uniform samplerCUBE environmentMap	: TEXUNIT4;

// inverse view matrix
uniform float3x4 inverseViewMatrix;

// material properties
uniform float mtlBumpMode;		// 0 = none, 1 = normal, 2 = parallax
uniform float mtlSpecMode;		// 0 = constant, 1 = map
uniform float mtlReflectMode;	// 0 = none, 1 = constant, 2 = map
uniform float3 mtlEmissive;
uniform float3 mtlAmbient;
uniform float4 mtlDiffuse;
uniform float4 mtlSpecularShininess; // rgb = specular, a = shininess
uniform float mtlReflectivity;

// scene properties
uniform float4 sceneFog; // rgb = color, a = density
uniform float3 sceneAmbient;

// light properties
static const int MAX_LIGHTS = 8;
uniform float lightCount;
uniform float lightType[MAX_LIGHTS]; // 0 = directional, 1 = spot
uniform float3 lightPosition[MAX_LIGHTS]; // doubles as direction for directional lights
uniform float3 lightAttenuation[MAX_LIGHTS]; // usage: x + y*D + z*D^2
uniform float3 lightAmbient[MAX_LIGHTS];
uniform float3 lightDiffuseSpecular[MAX_LIGHTS]; // diffuse and specular color

float3 rgbToXyz( float3 rgb ) {
	return rgb * 2.0f - 1.0f;

void main( in Input input, out float4 color : COLOR ) {
	input.normal = normalize( input.normal );

	// normal or parallax mapping
	if (mtlBumpMode > 0.0f) {
		// normalize these if needed
		input.tangent = normalize( input.tangent );
		input.binormal = normalize( input.binormal );

		// parallax mapping
		if (mtlBumpMode == 2.0f) {
			// apply parallax mapping
			float bumpScale = 0.05f;
			float fDepth = 0.0f;
			float2 vHalfOffset = float2( 0.0f, 0.0f );
			float2 eyeVector = float2( dot( input.position, input.tangent ),
									   dot( input.position, input.binormal ) );
			for (int i = 0; i < 3; ++i) {
				fDepth = (fDepth + (1.0f - tex2D( bumpMap, input.texCoord + vHalfOffset ).a)) * 0.5f;
				vHalfOffset = normalize( eyeVector ).xy * fDepth * bumpScale;
			input.texCoord += vHalfOffset;

		// apply normal mapping by sampling our bump map and multiplying by tbn
		float3 bump = rgbToXyz( tex2D( bumpMap, input.texCoord ).rgb );
		input.normal = normalize( input.tangent * bump.x +
								  input.binormal * bump.y +
								  input.normal * bump.z );

	// declare a float3 to hold our diffuse color
	float3 diffuse;

	// apply reflection mapping
	if (mtlReflectMode == 1.0f) {
		// get the reflection vector in eye space
		// multiply it by inverse view matrix to get it into world space
		float3 reflectCoord = reflect( input.position, input.normal );
		reflectCoord = mul( inverseViewMatrix, float4( reflectCoord, 0.0f ) ).xyz;
		// lerp based on reflectivity constant
		diffuse = lerp( tex2D( diffuseMap, input.texCoord ).rgb,
						texCUBE( environmentMap, reflectCoord ).rgb,
						mtlReflectivity );
	} else if (mtlReflectMode == 2.0f) {
		// get the reflection vector in eye space
		// multiply it by inverse view matrix to get it into world space
		float3 reflectCoord = reflect( input.position, input.normal );
		reflectCoord = mul( inverseViewMatrix, float4( reflectCoord, 0.0f ) ).xyz;
		// lerp based on sampled reflection map
		diffuse = lerp( tex2D( diffuseMap, input.texCoord ).rgb,
						texCUBE( environmentMap, reflectCoord ).rgb,
						tex2D( reflectMap, input.texCoord ).r );
	} else
		diffuse = tex2D( diffuseMap, input.texCoord ).rgb;

	// multiply diffuse by material diffuse
	diffuse *= mtlDiffuse.rgb;

	// declare a float4 to hold our specular color
	float4 specular;

	if (mtlSpecMode == 0.0f)
		specular = mtlSpecularShininess;
		specular = tex2D( specularMap, input.texCoord ).rgba;

	// now we compute lighting

	float3 intensity = mtlEmissive + mtlAmbient*sceneAmbient;

	float3 eyeDir = -normalize( input.position );
	for (int i = 0; i < lightCount && i < MAX_LIGHTS; ++i) {
		// for each light
		// first compute direction and attenuation
		float3 lightDir;
		float attenuation;
		if (lightType[i] == 0) {
			// directional light
			lightDir = -lightPosition[i];
			attenuation = 1.0f;
		} else {
			// point light
			lightDir = lightPosition[i] - input.position;
			float dist = length( lightDir );
			lightDir /= dist;
			attenuation = 1.0f/(lightAttenuation[i].x +
								lightAttenuation[i].y * dist +
								lightAttenuation[i].z * dist * dist);
		// compute the half vector for specularity
		float3 halfVec = normalize( (lightDir + eyeDir) * 0.5f );

		// compute N.L and N.H
		float nDotL = saturate( dot( input.normal, lightDir ) );
		float nDotH = saturate( dot( input.normal, halfVec ) );

		// determine the amount to increase the intensity by
		// we add ambient into this term because each light can contribute ambiently,
		// but only when an object is near the light; it attenuates like diffuse and specular
		// if overall ambient is wanted, use scene ambient
		float3 increase = mtlAmbient*lightAmbient[i] +
						  (diffuse*nDotL + specular.rgb*pow( nDotH, specular.a )*saturate( nDotL*5.0f )) * lightDiffuseSpecular[i];

		// weight by attenuation
		intensity += attenuation * increase;

	// compute the fog amount: e^-(density * z)
	float fogAmount = saturate( pow( 2.71828183f, -sceneFog.a * input.position.z ) );

	// finally, compute fragment color
	color = float4( lerp( intensity, sceneFog.rgb, fogAmount ), mtlDiffuse.a );

The errors are in the for loop for the lights where I try to access arrays of light parameters. In OpenGL NV30 Fragment Program, I'm getting: error C5043: profile requires index expression to be compile-time constant and error C5013: profile does not support "for" statements and "for" could not be unrolled. In OpenGL NV40 Fragment Program, I'm getting: error C6013: Only arrays of texcoords may be indexed in this profile, and only with a loop index variable What I'm trying to do is use static branching to loop through the arrays of light properties, but it appears that this doesn't work. Is there another way to do this? (Do I manually have to unroll the loop? I put a upper bound of MAX_LIGHTS on the loop, so I'd think that would fix issues, but apparently not...) EDIT: Well, it compiles if I do:
for (int i = 0; i < MAX_LIGHTS; ++i) {
	if (i >= lightCount)

Which I believe is still static branching. I can't test it on my current computer (older graphics card), but is this a good approach to take in terms of efficiency? If I do this, the loop is required to repeat the max number of times.

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V-man    813
You could do

for (int i = 0; i < lightCount; ++i)

or using break makes more sense than using continue.
for (int i = 0; i < MAX_LIGHTS; ++i)
if (i >= lightCount)

It should be alright since all fragments will execute the same number of loops.

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