CODEWITHSUNDEEP
opengl
MineR
MineR

Reputation: 2204

How do I specify Normals using GL_INT_2_10_10_10_REV in a VBO array?

I have normals which are (x,y,z) as 3 floats, and I want to pack these into a VBO array as GL_INT_2_10_10_10_REVs in order to reduce memory consumption on the graphics card. Can anyone provide an example of how to do this in C++ / C#?

The OpenGL documentation says you can do this - https://www.opengl.org/wiki/Vertex_Specification_Best_Practices

However, I can't find any examples of how to place the three floats (which can be positive or negative) into the single packed 4 byte structure.

Upvotes: 1

Views: 1097

Answers (2)

genpfault
genpfault

Reputation: 52167

Check the spec, section 10.3.8, "Packed Vertex Data Formats", page 343:

For INT_2_10_10_10_REV, the x, y and z components are represented as 10-bit signed two’s complement integer values and the w component is represented as a 2-bit signed two’s complement integer value.

Upvotes: 1

ratchet freak
ratchet freak

Reputation: 48226

You'll need to pack them in a bitfield that looks something like:

struct norm{
    int a:2; 
    int Z:10; 
    int y:10; 
    int X:10; //order may need to be different
}

ensure the field you put in are scaled to -512 to 511

Upvotes: 5

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