Why does my per-instance shader uniform affect every instance?

Plain 'uniform' is shared via the Material. To vary per node instance, declare with 'instance uniform' and set via set_instance_shader_parameter on the GeometryInstance3D.

How many instance uniforms can I have?

Limited by the platform — usually a handful per shader. Pack scalars into vec4 if you need many. Heavy data should still go through textures or buffers.

Can MultiMesh use this?

MultiMesh has its own per-instance data (color, custom_data). Use those rather than instance uniforms; they're designed for the workflow.

Fix: Godot 4 Per-Instance Shader Uniform Not Respected

Quick answer: Declare with instance uniform vec3 color; in the shader. Set via node.set_instance_shader_parameter("color", value). Each MeshInstance3D gets its own value while sharing the material.

You set a uniform per enemy. All enemies turn the same color. Plain uniform is shared via Material; instance uniform is per-node.

The Symptom

Per-instance uniform changes affect every node sharing the material. Want unique values per instance.

The Fix

shader_type spatial;

instance uniform vec3 enemy_color : source_color = vec3(1, 1, 1);

void fragment() {
    ALBEDO = enemy_color;
}

From script:

$Enemy1.set_instance_shader_parameter("enemy_color", Color.RED)
$Enemy2.set_instance_shader_parameter("enemy_color", Color.GREEN)

Each instance now renders with its own color while sharing the material asset.

Verifying

Spawn N instances with different parameter values. Each renders with its unique color. With plain uniform: all change to the last set.

“instance uniform. set_instance_shader_parameter. Per-node values.”

Related Issues

For shader uniform runtime, see runtime uniform. For MultiMesh instance color, see MultiMesh color.

Instance keyword. Per-node uniform.