layer_flutter(l, v) gives a scatter layer a per-leaf tremble. The vertex stage offsets each leaf by a phase taken from its own place on the card, so neighbouring leaves are never in step, and writes the result out as a varying the fragment stage uses to flash the leaf's pale underside as it turns - which is the part that reads, since a still frame of a tremble is a still frame of nothing. One uniform, one varying, no extra pass. And the sway itself was measured in METRES: hgt * hgt * 0.35 is right for a 40 cm flower and puts ten metres of sideways into a 14 m trunk, so every tall tree in the valley stood bent over like a fishing rod. It is a fraction of the model's own height now - the tip moves a few per cent of the tree whatever the tree is, and the base does not move at all. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
53 lines
1.8 KiB
GLSL
53 lines
1.8 KiB
GLSL
// a skinned glTF model (skin.ludic / actor.ludic): four joint influences per vertex
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// blended on the GPU, then one model matrix. Writes the same varyings as model.vert so
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// model.frag (lit) and shadow.frag (casters) shade it unchanged.
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layout(location = 0) in vec3 a_pos;
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layout(location = 1) in vec3 a_nrm;
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layout(location = 2) in vec2 a_uv;
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layout(location = 5) in vec4 a_joints; // integer indices, read as floats
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layout(location = 6) in vec4 a_weights;
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uniform mat4 u_model;
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uniform mat4 u_bones[48];
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uniform float u_skinned; // 0: a rigid model on the same path
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uniform mat4 u_view;
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uniform mat4 u_proj;
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uniform mat4 u_light_vp;
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#ifdef OUTLINE
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uniform float u_outline; // metres the shell is pushed out
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#endif
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out vec3 v_wpos;
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out vec3 v_nrm;
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out vec2 v_uv;
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out float v_seed;
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out vec2 v_rot;
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out float v_hull;
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out float v_quake; // only aspens quake; written so model.frag can read it
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void main() {
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mat4 m = u_model;
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if (u_skinned > 0.5) {
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mat4 sk = a_weights.x * u_bones[int(a_joints.x + 0.5)]
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+ a_weights.y * u_bones[int(a_joints.y + 0.5)]
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+ a_weights.z * u_bones[int(a_joints.z + 0.5)]
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+ a_weights.w * u_bones[int(a_joints.w + 0.5)];
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m = u_model * sk;
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}
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vec4 w = m * vec4(a_pos, 1.0);
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#ifdef OUTLINE
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// an inverted hull: the shell is pushed out along the world normal and drawn with the
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// front faces culled, so what survives is a rim of `u_outline` metres around the model
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w.xyz += normalize(mat3(m) * a_nrm) * u_outline;
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#endif
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v_wpos = w.xyz;
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v_nrm = normalize(mat3(m) * a_nrm);
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v_uv = a_uv;
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// model.frag scales the albedo by 0.85 + 0.3 * fract(seed * 7.13); this seed makes that 1
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v_seed = 0.0701;
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v_rot = vec2(0.0, 1.0);
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v_hull = 1.0;
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v_quake = 0.0;
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#ifdef SHADOW_PASS
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gl_Position = u_light_vp * w;
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#else
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gl_Position = u_proj * u_view * w;
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#endif
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}
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