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How can I 'add' several bump maps on each other

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Hi everybody, I have a a river with classic Env Bump Mapping with the following stages: Stage1: Texture Stage2: BumpMap Stage3: EnvMap. How can I put (add) several bump maps in stage 2 together (Fixed Function Pipeline!), maybe like a animated river with raindrops falling on it? The quantity of raindrops must be variable, so I want to make a animation set of waves (as bump maps) for a fallen raindrop and would like to dipose them all over the river. Can someone give me some idea/help? Thanks a lot!

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What exactly do you mean by "add"? You could average the bump maps through normal texture filtering I suppose.

Why do you want to do this with the fixed function pipeline? It's fairly complicated, and bump map support with the fixed function pipeline is a bit shakey as it is, without adding multiple maps together...

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Thanks for your quick reply!

With 'add' I mean, if I have one water bump map and another raindrop bump map, I would like to put them together at runtime, so there should be a raindrop wave on the water waves... everthing with bump maps.

I am just a beginner and would like learn all about FFP first before pixel shading a bit.

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Quote:
Original post by snipert
Thanks for your quick reply!

With 'add' I mean, if I have one water bump map and another raindrop bump map, I would like to put them together at runtime, so there should be a raindrop wave on the water waves... everthing with bump maps.

I am just a beginner and would like learn all about FFP first before pixel shading a bit.


The only meaningful way to "add" normal maps is to average the normal values that you sample from them, and then normalize. This is a single line of code in HLSL...I'm not even sure if you can do that at all with fixed-function processing.

Honestly I really don't think there's much point in continuing with FFP...shaders aren't the future, they're the present. Discrete GPU's haven't had fixed-function hardware since 2001 or so, and will emulate it with shaders. Which means you might as well go for the flexibility of shaders, since fixed-function won't be any quicker.

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