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particle: fix tail texcoords and transformVec4 input size

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Tail vertices V0/V1 read texture U/V from wrong addresses (no offset
from base instead of +8/+16 stride). Assembly reads 0x87D734/738 for
V0 and 0x87D73C/740 for V1, not the base 0x87D72C/730. This made both
base vertices share UVs, collapsing the texture and causing light beams
to taper to a point instead of maintaining width.

Also fix transformVec4 input: must be [4]f32 with w=0.0, not [3]f32.
The function reads all 4 components including [EDX+0xC]. Reading past
a 3-element array produced garbage w values that corrupted the velocity
transform, causing tail particles to extend wildly.

Fixed in both SSE and reference implementations.
This commit is contained in:
MarcelineVQ
2026-03-24 22:01:32 -07:00
parent 9a3e06a7cc
commit e78ebfd74d
4 changed files with 17 additions and 53 deletions
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src/transform44/particle_sse_reference.zig
+5 -5
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@@ -480,7 +480,7 @@ export fn renderParticleSprites_REF(emitter: u32, particle_data: u32, vertex_buf
}
// Transform negated velocity through world matrix
var neg_vel = [3]f32{ neg_vel_x, neg_vel_y, neg_vel_z };
var neg_vel = [4]f32{ neg_vel_x, neg_vel_y, neg_vel_z, 0.0 };
var transformed_vel: [4]f32 = undefined;
_ = transformVec4(@intFromPtr(&transformed_vel), @intFromPtr(&neg_vel), G.world_matrix);
@@ -500,12 +500,12 @@ export fn renderParticleSprites_REF(emitter: u32, particle_data: u32, vertex_buf
// Vertex 0: worldPos - perp
emitVertex(vb, world_pos[0] - perp_y, perp_x + world_pos[1], world_pos[2], color_value,
rf32(G.sprite_tex_u) * tex_su + tail_tex_u,
rf32(G.sprite_tex_v) * tex_sv + tail_tex_v);
rf32(G.sprite_tex_u + 8) * tex_su + tail_tex_u,
rf32(G.sprite_tex_v + 8) * tex_sv + tail_tex_v);
// Vertex 1: worldPos + perp
emitVertex(vb, world_pos[0] + perp_y, world_pos[1] - perp_x, world_pos[2], color_value,
rf32(G.sprite_tex_u) * tex_su + tail_tex_u,
rf32(G.sprite_tex_v) * tex_sv + tail_tex_v);
rf32(G.sprite_tex_u + 16) * tex_su + tail_tex_u,
rf32(G.sprite_tex_v + 16) * tex_sv + tail_tex_v);
// Vertex 2: worldPos + vel - perp
emitVertex(vb, tx + world_pos[0] - perp_y, ty + world_pos[1] + perp_x, vel_z, color_value,
rf32(G.tail_tex_u0) * tex_su + tail_tex_u,