From fc22d14dfdb041797db66a9232b3beb06fada08d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Manuel=20Tom=C3=A1s?= <jtomas1815@gmail.com>
Date: Sat, 30 Jan 2021 18:18:23 -0300
Subject: Refactor curve drawing functionality

---
 src/lib.rs | 149 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 149 insertions(+)

(limited to 'src/lib.rs')

diff --git a/src/lib.rs b/src/lib.rs
index d6a1374..db5d42f 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -4,6 +4,10 @@ mod poly;
 use lerp::Lerp;
 use poly::Poly;
 
+use std::ffi::{CStr, CString};
+
+use gl::types::*;
+
 pub struct Bezier {
     pub degree: usize,
     pub vx: Vec<f32>,
@@ -68,4 +72,149 @@ impl Bezier {
         }
         s
     }
+
+    pub fn draw(&self) {
+        let vertex_shader_source = b"
+        #version 410 core
+        layout (location = 0) in vec3 aPos;
+    
+        void main() {
+            gl_Position = vec4(aPos.xyz, 1.0);
+        }
+        "
+        .to_vec();
+    
+        let fragment_shader_source = format!(
+            "
+        #version 410 core
+        out vec4 FragColor;
+    
+        float vx[{s}] = float[{s}]({vx});
+        float vy[{s}] = float[{s}]({vy});
+    
+        float px[{sx}] = float[{sx}]({px});
+        float py[{sy}] = float[{sy}]({py});
+    
+        float dpx[{dsx}] = float[{dsx}]({dpx});
+        float dpy[{dsy}] = float[{dsy}]({dpy});
+    
+        float thr = 32;
+        float step_size = 10;
+        float inf = 1000000;
+    
+        float eval_px(float t) {{
+            float result = 0.0;
+            for (int i = 0; i < {sx}; i++) {{
+              result += px[i] * pow(t, i);
+            }}
+            return result;
+        }}
+    
+        float eval_py(float t) {{
+            float result = 0.0;
+            for (int i = 0; i < {sy}; i++) {{
+              result += py[i] * pow(t, i);
+            }}
+            return result;
+        }}
+    
+        float eval_dpx(float t) {{
+            float result = 0.0;
+            for (int i = 0; i < {dsx}; i++) {{
+              result += dpx[i] * pow(t, i);
+            }}
+            return result;
+        }}
+    
+        float eval_dpy(float t) {{
+            float result = 0.0;
+            for (int i = 0; i < {dsy}; i++) {{
+              result += dpy[i] * pow(t, i);
+            }}
+            return result;
+        }}
+    
+        float control(vec2 pos) {{
+          float closest = inf;
+          for (int i = 0; i < {s}; i++) {{
+            float d = distance(pos, vec2(vx[i], vy[i]));
+            if (d < closest) {{
+              closest = d;
+            }}
+          }}
+          return 1 - closest / thr;
+        }}
+    
+        float inside(vec2 pos) {{
+          float closest = inf;
+          float t = 0.0;
+          float dstep = 0.0;
+          while (t < 1.0 - dstep) {{
+            dstep = step_size / length(vec2(eval_dpx(t), eval_dpy(t)));
+            float step = t + dstep;
+            vec2 a = vec2(eval_px(t), eval_py(t));
+            vec2 b = vec2(eval_px(step), eval_py(step));
+            float c = pow(length(a - b), 2);
+            float d = distance(pos, a + clamp(dot(pos - a, b - a) / c, 0, 1) * (b - a));
+            if (d < closest) {{
+              closest = d;
+            }}
+            t = step;
+          }}
+          return 1 - closest / thr;
+        }}
+    
+        void main() {{
+          float r = inside(gl_FragCoord.xy);
+          float c = control(gl_FragCoord.xy);
+          FragColor = vec4(r, c, 0.0, 1.0);
+        }}
+        ",
+            s = self.degree,
+            vx = self.show_x(),
+            vy = self.show_y(),
+            px = &self.px,
+            py = &self.py,
+            sx = self.px.degree() + 1,
+            sy = self.py.degree() + 1,
+            dpx = &self.dpx,
+            dpy = &self.dpy,
+            dsx = self.dpx.degree() + 1,
+            dsy = self.dpy.degree() + 1,
+        )
+        .into_bytes();
+    
+        let shader_program: GLuint;
+        unsafe {
+            let vertex_shader = shader_from_source(
+                &CString::from_vec_unchecked(vertex_shader_source),
+                gl::VERTEX_SHADER,
+            );
+            let fragment_shader = shader_from_source(
+                &CString::from_vec_unchecked(fragment_shader_source),
+                gl::FRAGMENT_SHADER,
+            );
+            shader_program = gl::CreateProgram();
+            gl::AttachShader(shader_program, vertex_shader);
+            gl::AttachShader(shader_program, fragment_shader);
+            gl::LinkProgram(shader_program);
+            gl::DeleteShader(vertex_shader);
+            gl::DeleteShader(fragment_shader);
+            gl::UseProgram(shader_program);
+        }
+    }
 }
+
+fn shader_from_source(source: &CStr, shader_type: GLenum) -> GLuint {
+    unsafe {
+        let shader: GLuint = gl::CreateShader(shader_type);
+        gl::ShaderSource(shader, 1, &source.as_ptr(), std::ptr::null());
+        gl::CompileShader(shader);
+        let mut success: gl::types::GLint = 1;
+        gl::GetShaderiv(shader, gl::COMPILE_STATUS, &mut success);
+        if success == 0 {
+            println!("Compilation error: {}", source.to_str().unwrap());
+        }
+        shader
+    }
+}
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