Add a uModelViewProjectionMatrix uniform

[JetStarBlues]

Add a uModelViewProjectionMatrix uniform

How would this new feature help increase access to p5.js?

Makes the modelViewProjection matrix available as a uniform for users to use in their shader programs.

As a result, the minimum code that a user needs to write in their program decreases (and the final code is more performant).

Most appropriate sub-area of p5.js?

• WebGL

Feature enhancement details:

The modelViewProjection (mvp) matrix is needed by all vertex shaders that seek to display 3D coordinates on a 2D screen.

Currently, only the uModelViewMatrix and uProjectionMatrix are provided by p5 for use in shader programs. As a result, the mvpMatrix must be calculated in the vertex shader.

attribute vec3 aPosition;

uniform mat4 uModelViewMatrix;
uniform mat4 uProjectionMatrix;

void main() {

  vec4 position = vec4(aPosition, 1.0);

  gl_Position = uProjectionMatrix * uModelViewMatrix * position;
}

If available as a uniform, vertex shaders can be simplified to:

attribute vec3 aPosition;

uniform mat4 uModelViewProjectionMatrix;

void main() {

  vec4 position = vec4(aPosition, 1.0);

  gl_Position = uModelViewProjectionMatrix * position;
}

This simplification makes the vertex shader code less dense.

Since currently this calculation is done per vertex, there is also a performance boost earned by doing this calculation once on the CPU and passing the value on to the shader as a uniform.

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More discussion on this can be found on the related issue on the p5.js-website repo.
This discussion is also related.
A live example of this workflow can be found here.