From 5cd440b3a3b4a0625de72c1fdbfba2c92ae6b50e Mon Sep 17 00:00:00 2001
From: WormHeamer
Date: Sat, 19 Jul 2025 17:40:20 -0400
Subject: particles!

---
 Makefile        |  2 +-
 shader/tri.frag | 12 +++++++++++-
 shader/tri.vert | 26 ++++++++++++++++++++++----
 3 files changed, 34 insertions(+), 6 deletions(-)

diff --git a/Makefile b/Makefile
index bf013d0..0689789 100644
--- a/Makefile
+++ b/Makefile
@@ -11,7 +11,7 @@ clean:
 	rm -fv ${EXE} ${SPIRV}
 
 ${EXE}: *.c
-	${CC} -Os -Wall -std=c23 $< -o $@ -lSDL3 -lm
+	${CC} -Os -Wall -std=c23 $< -o $@ -lSDL3 -lm -fsanitize=undefined
 
 %.spv: %
 	glslc -O -c "$<" -o "$@"
diff --git a/shader/tri.frag b/shader/tri.frag
index dea0868..f67a4e0 100644
--- a/shader/tri.frag
+++ b/shader/tri.frag
@@ -1,9 +1,19 @@
 #version 450
 
 layout(location = 0) in vec2 uv;
+layout(location = 1) in vec4 in_color;
+layout(location = 2) flat in int type;
+
 layout(location = 0) out vec4 out_color;
 
 void main(void) {
 	float n = 2 * length(uv - 0.5);
-	out_color = vec4(vec3(uv, 1) * (1.75 - n), float(n<1));
+	switch (type) {
+	case 0:
+		out_color = vec4(in_color.rgb, in_color.a * float(n<1));
+		break;
+	case 1:
+		out_color = vec4(in_color.rgb, in_color.a * (max(0.25 - n, 0) + max(1 - n, 0)) * 0.5);
+		break;
+	}
 }
diff --git a/shader/tri.vert b/shader/tri.vert
index 750b2a3..dc7389c 100644
--- a/shader/tri.vert
+++ b/shader/tri.vert
@@ -4,11 +4,29 @@ layout(set = 1, binding = 0) uniform UBO {
 	mat4 camera;
 };
 
-layout(location = 0) in vec2 in_pos;
-layout(location = 1) in vec2 in_uv;
 layout(location = 0) out vec2 out_uv;
+layout(location = 1) out vec4 out_color;
+layout(location = 2) flat out int out_type;
+
+struct Particle {
+	vec2 pos;
+	float radius, life;
+	vec3 color;
+	int type;
+};
+
+layout(binding = 0) buffer Particles {
+	Particle pts[];
+};
+
+uint tri_idx[6] = { 0, 1, 2, 3, 2, 1 };
+vec2 tri_pos[4] = { {0,0}, {1,0}, {0,1}, {1,1} };
 
 void main() {
-	gl_Position = camera * vec4(in_pos, 0.0, 1.0);
-	out_uv = in_uv;
+	Particle p = pts[gl_VertexIndex / 6];
+	vec2 ofs = tri_pos[tri_idx[gl_VertexIndex % 6]];
+	out_uv = ofs;
+	gl_Position = camera * vec4((ofs - 0.5) * p.radius * p.life + p.pos, 0.0, 1.0);
+	out_color = vec4(p.color,1);
+	out_type = p.type;
 }
-- 
cgit 1.4.1-2-gfad0