From 64c94fd1b8897ae266b5c5142729f6d25f805daf Mon Sep 17 00:00:00 2001
From: nothke <nothke@gmail.com>
Date: Wed, 12 Jun 2024 01:18:22 +0200
Subject: [PATCH] Circle! (black and 8 sided)

---
 src/main.zig | 57 ++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 46 insertions(+), 11 deletions(-)

diff --git a/src/main.zig b/src/main.zig
index 79f6e74..20e9807 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -24,25 +24,60 @@ export fn init() void {
 
     std.log.info("Vertex buffers len: {}", .{state.bind.vertex_buffers.len});
 
-    var triangleVerts = [_]f32{
-        // positions     colors
-        0.0,  0.5,  0.5, 1.0, 0.0, 0.0, 1.0,
-        0.5,  -0.5, 0.5, 0.0, 1.0, 0.0, 1.0,
-        -0.5, -0.5, 0.5, 0.0, 0.0, 1.0, 1.0,
-        0.7,  0.5,  0.5, 0.0, 1.0, 0.0, 1.0,
-    };
+    const vertexCount = 8;
+    const radius: f32 = 0.4;
+
+    const cX: f32 = 0;
+    const cY: f32 = 0;
+
+    const attributesCount = 7;
+
+    var triangleVerts = std.mem.zeroes([vertexCount * attributesCount]f32);
+
+    const angleDiff: f32 = 1 / @as(f32, @floatFromInt(vertexCount));
+
+    for (0..vertexCount) |i| {
+        const pi: f32 = @floatCast(std.math.pi);
+        const angle: f32 = @as(f32, @floatFromInt(i)) * angleDiff * pi * 2;
+
+        const x = radius * @cos(angle) + cX;
+        const y = radius * @sin(angle) + cY;
+
+        const si = i * attributesCount;
+        triangleVerts[si + 0] = x;
+        triangleVerts[si + 1] = y;
+        triangleVerts[si + 2] = 0.5;
+    }
+
+    // var triangleVerts = [_]f32{
+    //     // positions     colors
+    //     0.0,  0.5,  0.5, 1.0, 0.0, 0.0, 1.0,
+    //     0.5,  -0.5, 0.5, 0.0, 1.0, 0.0, 1.0,
+    //     -0.5, -0.5, 0.5, 0.0, 0.0, 1.0, 1.0,
+    //     0.7,  0.5,  0.5, 0.0, 1.0, 0.0, 1.0,
+    // };
 
     state.bind.vertex_buffers[0] = sg.makeBuffer(.{
         .data = sg.asRange(&triangleVerts),
     });
 
-    const indexBuffer = [_]u16{
-        0, 1, 2,
-        0, 3, 1,
-    };
+    const trisCount = vertexCount - 2;
 
+    var indexBuffer: [trisCount * 3]u16 = undefined;
     state.indexCount = indexBuffer.len;
 
+    // const indexBuffer = [_]u16{
+    //     0, 1, 2,
+    //     0, 2, 3,
+    // };
+
+    for (0..trisCount) |tri| {
+        const triu: u16 = @intCast(tri);
+        indexBuffer[tri * 3 + 0] = 0;
+        indexBuffer[tri * 3 + 1] = triu + 1;
+        indexBuffer[tri * 3 + 2] = triu + 2;
+    }
+
     state.bind.index_buffer = sg.makeBuffer(.{
         .type = .INDEXBUFFER,
         .data = sg.asRange(&indexBuffer),