vaPosition

Danger

This attribute only works with the “core profile” in Minecraft 1.17 and newer. It is recommended to use the “compatibility profile” with Iris for better support.

in vec3 vaPosition;

Valid Programs: all gbuffers/shadow

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The vertex position attribute. For terrain this is relative to the chunk and you must add chunkOffset as shown below:

vec3 model_pos = vaPosition + chunkOffset;
vec4 view_pos = modelViewMatrix * vec4(model_pos, 1.0);
vec4 clip_pos = projectionMatrix * view_pos;

gl_Position = clip_pos;

For all other geometry, vaPosition directly stores the model space position. In either case, the model space position is equivalent to gl_Vertex.xyz from the compatibility profile.

vec3 model_pos = gl_Vertex.xyz;
vec4 view_pos = gl_ModelViewMatrix * vec4(model_pos, 1.0);
vec4 clip_pos = gl_ProjectionMatrix * view_pos;

gl_Position = clip_pos;