1 files changed, 151 insertions, 0 deletions
diff --git a/graphics.go b/graphics.go
new file mode 100644
index 0000000..812be3a
--- /dev/null
+++ b/graphics.go
@@ -0,0 +1,151 @@
+// vim: shiftwidth=4 tabstop=4 noexpandtab
+
+package main
+
+import (
+	"fmt"
+	"log"
+	"strings"
+
+	"github.com/go-gl/gl/v4.6-core/gl"
+	"github.com/go-gl/glfw/v3.3/glfw"
+)
+
+var (
+	// a single triangle
+	triangle = []float32{
+		 0.0,  0.5,  0.0,
+		-0.5, -0.5,  0.0,
+		 0.5, -0.5,  0.0,
+	}
+)
+
+const (
+	WINDOW_WIDTH  = 500
+	WINDOW_HEIGHT = 500
+	WINDOW_TITLE = "stlscope"
+
+	// vertex shader to draw points
+	VERTEX_SHADER = `
+        #version 410
+        in vec3 vp;
+        void main() {
+            gl_Position = vec4(vp, 1.0);
+        }
+    ` + "\x00"
+
+	// fragment shader to draw surfaces
+	FRAGMENT_SHADER = `
+        #version 410
+        out vec4 frag_colour;
+        void main() {
+            frag_colour = vec4(0, 0, 1, 1);  // RGBA color format
+        }
+    ` + "\x00"
+)
+
+func initGlfw() *glfw.Window {
+	log.Println("GLFW init")
+
+	if err := glfw.Init(); err != nil {
+		panic(err)
+	}
+
+	glfw.WindowHint(glfw.Resizable, glfw.False)
+	glfw.WindowHint(glfw.ContextVersionMajor, 4)
+	glfw.WindowHint(glfw.ContextVersionMinor, 6)
+	glfw.WindowHint(glfw.OpenGLProfile, glfw.OpenGLCoreProfile)
+	glfw.WindowHint(glfw.OpenGLForwardCompatible, glfw.True)
+	glfw.WindowHint(glfw.Samples, 16)  // anti-aliasing
+
+	window, err := glfw.CreateWindow(WINDOW_WIDTH, WINDOW_HEIGHT, WINDOW_TITLE, nil, nil)
+	if err != nil {
+		panic(err)
+	}
+	window.MakeContextCurrent()
+
+	return window
+}
+
+// initOpenGL initializes OpenGL and returns an intiialized program
+func initOpenGL() uint32 {
+	log.Println("OpenGL init")
+
+	if err := gl.Init(); err != nil {
+		panic(err)
+	}
+	version := gl.GoStr(gl.GetString(gl.VERSION))
+	log.Println("OpenGL version", version)
+
+	vertexShader, err := compileShader(VERTEX_SHADER, gl.VERTEX_SHADER)
+	if err != nil {
+		panic(err)
+	}
+	fragmentShader, err := compileShader(FRAGMENT_SHADER, gl.FRAGMENT_SHADER)
+	if err != nil {
+		panic(err)
+	}
+
+	prog := gl.CreateProgram()
+	gl.AttachShader(prog, vertexShader)
+	gl.AttachShader(prog, fragmentShader)
+	gl.LinkProgram(prog)
+	return prog
+}
+
+func draw(vao uint32, window *glfw.Window, program uint32) {
+	gl.Clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT)
+	gl.UseProgram(program)
+
+	gl.BindVertexArray(vao)
+	gl.DrawArrays(gl.TRIANGLES, 0, int32(len(triangle)/3))
+
+	glfw.PollEvents()
+	window.SwapBuffers()
+}
+
+// makeVao initializes and returns a vertex array from the points provided.
+func makeVao(points []float32) uint32 {
+	log.Println("Creating VAO")
+
+	// start with vertex buffer object (VBO):
+	var vbo uint32  // VBO ID
+	gl.GenBuffers(1, &vbo)
+	gl.BindBuffer(gl.ARRAY_BUFFER, vbo)
+	gl.BufferData(gl.ARRAY_BUFFER, 4*len(points), gl.Ptr(points), gl.STATIC_DRAW)
+
+	// vertex array objects (VAO) are a feature of newer GL implementations:
+	var vao uint32  // VAO ID
+	gl.GenVertexArrays(1, &vao)
+	gl.BindVertexArray(vao)
+	gl.EnableVertexAttribArray(0)
+	gl.BindBuffer(gl.ARRAY_BUFFER, vbo)
+	gl.VertexAttribPointer(0, 3, gl.FLOAT, false, 0, nil)  // tell GL to use 3D float vectors
+
+	return vao
+}
+
+func compileShader(source string, shaderType uint32) (uint32, error) {
+	log.Println("Compiling shader")
+
+	shader := gl.CreateShader(shaderType)
+
+	csources, free := gl.Strs(source)
+	gl.ShaderSource(shader, 1, csources, nil)
+	free()
+	gl.CompileShader(shader)
+
+	var status int32
+	gl.GetShaderiv(shader, gl.COMPILE_STATUS, &status)
+	if status == gl.FALSE {
+		var logLength int32
+		gl.GetShaderiv(shader, gl.INFO_LOG_LENGTH, &logLength)
+
+		log := strings.Repeat("\x00", int(logLength+1))
+		gl.GetShaderInfoLog(shader, logLength, nil, gl.Str(log))
+
+		return 0, fmt.Errorf("failed to compile %v: %v", source, log)
+	}
+
+	return shader, nil
+}