Passing Array to Vertex Shader as Attribute

Question

I am doing some LBS, and I need to use more than 4 weights, and indices (Let's say I need 60 float values, and 60 int values).

I am using GLSL version 1.30, so I cannot use Shader Storage Buffer Object. Since this weight, and index information will be different for each vertex, cannot use uniform, and I guess there is no way to define an array with a fixed size (for example float arr[16]) if you are not using uniform. Additionally, for attribute inputs, I can only use vec/mat 2,3 or 4.

So, do you have any idea how I can solve this problem?

How can you need 120 values for each one, a vertex? I mean, why? — Sung
– Sung, Commented Jul 30, 2015 at 22:10
It looks you need 1 weight for 1 vertex but you need at least 15 vertices(vec4) which are float vert[60] with float weight[60] and int indices[60] right? — Sung
– Sung, Commented Jul 30, 2015 at 22:22

dari · Accepted Answer · 2015-07-30 21:43:22Z

2

A first approach would be to just pass them as normal vertex attributes. There is though a driver specific maximum number of vertex attributes.

A better approach, that should work with every driver and with an arbitrary amount of attributes (not infinite, but pretty many) is, to store the vertex attributes in a texture.

A simple setup would be to create a NxM texture, where N=#vertex_attributes and M=#vertices. Each vertex has then only one attribute, that indicates a line of the texture. In the vertex shader you can then read one line of the texture per vertex and have all your attributes.

answered Jul 30, 2015 at 21:43

dari

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2 Comments

ciyo Over a year ago

Thank you, it is a good idea. But, could you give me a little more idea about how I can generate a texture, and iterate it in the shader?

dari Over a year ago

Creating a texture can be done with the following comands: glGenTextures(...), glTexImage2D(...) You should find plenty of tutorial how to use them. Accessing a texture in shader can be done with texelFetch(...), texture(...) again, just look at basic texture tutorials.

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