Using a shader on the whole GPUParticles2D system rather than the individual particles

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1

Godot Version

4.2

Question

I added this canvas_item shader to the CanvasItem Material:

shader_type canvas_item;

uniform float skew_amount : hint_range(-1.0, 1.0);

void vertex() {
// Apply skewing to vertex positions
VERTEX.x += VERTEX.y * skew_amount;
}

But that skews each individual particle…

I also tried this:

shader_type canvas_item;

uniform float skew_amount : hint_range(-1.0, 1.0);

void vertex() {
  // Define skew matrix
  mat4 skew_matrix = mat4(
      vec4(1.0, skew_amount, 0.0, 0.0),
      vec4(0.0, 1.0, 0.0, 0.0),
      vec4(0.0, 0.0, 1.0, 0.0),
      vec4(0.0, 0.0, 0.0, 1.0)
  );

  // Transform vertex to clip space (optional)
  vec4 vertex_clip = MODEL_MATRIX * vec4(VERTEX.xy, 0.0, 1.0);

  // Apply skew using skew matrix
  vertex_clip = skew_matrix * vertex_clip;

  // Set vertex position (already transformed or not)
  VERTEX = vertex_clip.xy;
}

Which also skews each particle individually.

Finally, I tried this:

shader_type canvas_item;

uniform float skew_amount : hint_range(-1.0, 1.0);

void vertex() {
  // Transform vertex to clip space
  vec4 vertex_clip = MODEL_MATRIX * vec4(VERTEX.xy, 0.0, 1.0);

  // Apply skewing using y component
  vertex_clip.x += vertex_clip.y * skew_amount;

  // Set vertex position (already transformed)
  VERTEX = vertex_clip.xy;
}

But still the same result… Each particle got skewed individually…

So, how do I skew the entire particle system? :slight_smile:

3

interesting shader you are working with, but i fail to understand what do you mean by skew whole gpu particle2d

i tried 2 of the shader you tested with at my end
image
image
based on the blue rectangle it should be skewing the gpuparticle2d

if possible, provide what it should look like

4

No skew:

Wrong skew with shader (the particle is skewed before other operations, like angular velocity):

Desired effect (everything is skewed as a whole after other operations, like angular velocity):

5

the last one is basically the first one but skewed with node2d’s skew?

6

Yes, the last one is the first one with skew. Those examples aren’t done with GPUParticle2D. I just did those to show what I mean.

7

Bumpsie