From 57155f2c36b3a4069d3f27b27e4caf4420a76315 Mon Sep 17 00:00:00 2001
From: Loek Le Blansch <loek@pipeframe.xyz>
Date: Thu, 13 Jun 2024 13:58:37 +0200
Subject: effect kinda working

---
 consts.h   |  3 +++
 fb.c       |  4 ++--
 pass1.frag | 31 +++++++++++++++++++++++++------
 3 files changed, 30 insertions(+), 8 deletions(-)

diff --git a/consts.h b/consts.h
index ea4dbbe..6acab4c 100644
--- a/consts.h
+++ b/consts.h
@@ -8,4 +8,7 @@
 #define U_LOC_PASS1 2
 #define U_LOC_WINDOW 3
 
+#define PI 3.141592653589793
+#define PI_2 6.283185307179586
+
 #endif
diff --git a/fb.c b/fb.c
index 479808c..f072ad9 100644
--- a/fb.c
+++ b/fb.c
@@ -16,8 +16,8 @@ GLuint init_fb() {
 	glGenTextures(1, &buffer);
 	glBindTexture(GL_TEXTURE_2D, buffer);
 	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, RES_H, RES_V, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
-	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
-	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
 	glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, buffer, 0);
 	if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
 		die("can't initialize framebuffer??\n");
diff --git a/pass1.frag b/pass1.frag
index 784a9a2..8917b61 100644
--- a/pass1.frag
+++ b/pass1.frag
@@ -9,16 +9,35 @@ layout(location = U_LOC_TIME) uniform float time;
 layout(location = U_LOC_PASS1) uniform sampler2D buf;
 ivec2 res = ivec2(RES_H, RES_V);
 
+const float step = 0.04;
+const float turns = 9.0;
+
 void main() {
-	vec2 point = vec2(sin(time), cos(time)) * 0.7;
-	point.x *= float(res.y) / float(res.x); // adjust for aspect ratio
-	point = ((point + 1.0) / 2.0) * res.xy; // convert to screen coords
+	vec2 uv = gl_FragCoord.xy / res.xy;
 	float r = 20.0; // circle radius
+	
+	vec2 norm = (uv - 0.5) * 2.0;
+	norm.x *= float(res.x) / float(res.y); // adjust for aspect ratio
+
+	float offset = time * 7.0;
+
+	float mag = 1.3 + 0.5 * sin(2 * time);
+	float size = 0.4 + 0.1 * sin(3 * time);
 
 	color = vec4(0.0);
-	if (length(gl_FragCoord.xy - point) < r)
-		color = vec4(1.0);
 
-	color += texture(buf, gl_FragCoord.xy / res.xy) * 0.95;
+	for (float t = 0.0; t < PI_2; t += step) {
+		// <https://www.desmos.com/calculator/e0kq6z1ndd>
+		vec2 f = vec2(
+			cos(t) + mag * cos(turns * t + offset),
+			sin(t) + mag * sin(turns * t + offset)
+		);
+		f *= size;
+		if (length(f - norm) < 0.01) {
+			color = vec4(1.0, 1.0, 1.0, 1.0);
+		}
+	}
+
+	color += texture(buf, ((uv - 0.5) * 0.99) + 0.5) * 0.97;
 }
 
-- 
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