Crosscheck: Per-Instance Variables, and Shaders

So, mainly to make sure I'm following this correctly, I did a bit of research and came up with

A (mostly crappy) Object To Shader Code-flow Example

So let me start out by saying that the net effect of this particular little line of hackishness is not likely to blow a bunch of air up anyones skirts. The example provied is arbitrarily small to make it as simple as possible to follow the logic, not so it'll be a drop-in totally usefull rescource.

That being said, just as with datablocks, theres times you'll want to change stock behavior from per type-of-asset, to per-asset, and that's where this comes in. (couple things I have in mind, in case someone wants to turn arround and also do some leg-work are: paletswapping on a texture based on the current mObjectColor setup, multplying the alphachanel of a second damage texture laying on top of a healthy texture based on the object's health so it get's dirtier/more cracked/bloodier, whatever based on the damage it's taken, or simply proprly scrolling tank-treds basedon the tanks movement speed. The only one I'm personally working on atm is the first, so the rest would be things to get back to at some point.)

Now then, for clarity, we'll be starting our code-journey at the material end, and work our way back from there with the following setup:

Engine:
Materials.cc/cpp

void Material::setShaderConstants( const SceneGraphData &sgData, U32 stageNum )
{
...
   if (!mOverrideColor)
       GFX->setPixelShaderConstF( PC_MAT_SPECCOLOR, (float*)&specular[stageNum], 1 );
   else
	   GFX->setPixelShaderConstF( PC_MAT_SPECCOLOR, (float*)&sgData.mObjectColor, 1 );
...
}

Script:

new Material(buggy_body001a)
{
...
	OverrideColor = true;
...
};

This is to ensure that only those flagged materials update, since you'll likely have a few you don't want to bother with.

now sgData get's it's info from struct RenderInst, so we parse in a ColorF mObjectColor; into renderInstMgr.h

In order to have a point of reffernece for that RenderInst, we go into
tsMesh.cc/cpp

void TSMesh::render(S32 frame, S32 matFrame, TSMaterialList * materials)
{
   if( vertsPerFrame <= 0 ) return;

   RenderInst *coreRI = gRenderInstManager.allocInst();
   coreRI->type = RenderInstManager::RIT_Mesh;
   coreRI->calcSortPoint( smObject, smSceneState->getCameraPosition() );

   if (smObject) coreRI->mObjectColor = smObject->mObjectColor; //goes fatal if not assigned...
...
}

smObject refferences a sceneObject (wich is one of the reasons it looks like I'll be neeing to upate the guiobjectview this end once the actual palletswappers written on out, but that's beyond the scope of this case study), so we need to add yet another mObjectColor to that definition, as well as add in:

void SceneObject::initPersistFields()
{
...
   addField("ObjectColor", TypeColorF, Offset(mObjectColor, SceneObject));
...
}

so that we can dynamicly update our values.

Wich brings us to the highly unoptimised quick-hack finish of the lil example:

U32 GameBase::packUpdate(NetConnection *, U32 mask, BitStream *stream)
{
...
   stream->writeFloat(mObjectColor.red, 7);
   stream->writeFloat(mObjectColor.green, 7);
   stream->writeFloat(mObjectColor.blue, 7);
   stream->writeFloat(mObjectColor.alpha, 7);
...
}

void GameBase::unpackUpdate(NetConnection *con, BitStream *stream)
{
...
   mObjectColor.red = stream->readFloat(7);
   mObjectColor.green = stream->readFloat(7);
   mObjectColor.blue = stream->readFloat(7);
   mObjectColor.alpha = stream->readFloat(7);
...
}

aaand finally, what's an explaination involving shaders without crappy programmer-art:

http://img507.imageshack.us/my.php?image=23793758sm9.jpg
http://img507.imageshack.us/my.php?image=35320906rx6.jpg
http://img509.imageshack.us/my.php?image=47990172qb3.jpg


Miss anything? There a cleaner way to accomplish this? Any tips on refining things for the stated three intended usage cases?