mikel wrote:
But, how to control/change ambient color?
If you don't have much graphics programming experience yet, the easiest way is to really exchange the ambient cube map.
HDRShop (version 1 is free for non-commercial use) with its diffuse convolution and
CubeMapGen are very useful there. It is possible to implement a completely different ambient model but that requires shader and in some cases pipeline changes. Horde is a generic renderer, it does not dictate which rendering techniques should be used and the cube map based ambient in the demos is just provided as a sample implementation.
mikel wrote:
Second question
Horde can sort meshes by materials to minimize state changes. It does not use instancing at the moment as draw calls are usually faster in GL than in d3d9, so the benefit for GL would be less. Anyway, even with all engine optimizations, draw calls have a considerable performance overhead, both on the CPU and GPU side. So if you can somehow merge several of your tiny objects into single meshes, you will definitely get a performance benefit if you have a lot of them.