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androidopengl-esvboglslesvao
Mohamed
Mohamed

Reputation: 347

Android OpenGL ES2 Many textures for one VBO

I have many fixed objects like terrains and buildings and I want to merge them all in one VBO to reduce draw calls and enhance performance when there are too many objects, I load textures and store their ids in an array, my question is can I bind textures to that one VBO or must I make a separate VBO for each texture? or can I make many glDrawArrays for one VBO based on offset and length, if I can do that will this be smooth and well performed?

Upvotes: 0

Views: 136

Answers (2)

codetiger
codetiger

Reputation: 2779

There are couple of standard techniques that many Game Engines perform to achieve low draw calls.

Batching: This technique combines all objects referring to same material and combines them into one mesh. The objects does not even have to be static. If they are dynamic you can still batch them by passing the Model Matrix array.

Texture Atlas: Creating texture atlas for all static meshes is the best way as said in the other answer. However, you'll have to do a lot of work for combining the textures efficiently and updating their UVs accordingly.

Upvotes: 0

Reto Koradi
Reto Koradi

Reputation: 54592

In ES 2.0, if you want to use multiple textures in a single draw call, your only good option is to use a texture atlas. Essentially, you store the texture data from multiple logical textures in a single OpenGL texture, and the texture coordinates are chosen so that the desired texture data is used for each primitive. This could be done by adjusting the original texture coordinates, or by feeding an id into the shader and applying an offset to the texture coordinates based on the id.

Of course you can use multiple glDrawArrays() calls for a single VBO, with binding a different texture between them. But that goes against your goal of reducing the number of draw calls. You should certainly make sure that the number of draw calls really is a bottleneck for you before you spend a lot of time on these types of optimizations.

In more advanced versions of OpenGL you have additional features that can help with this use case, like array textures.

Upvotes: 1

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