From 91763a9e1a4a3d5f67696c5d4babcafe09851aa5 Mon Sep 17 00:00:00 2001
From: faiface <faiface@ksp.sk>
Date: Wed, 23 Nov 2016 15:59:21 +0100
Subject: [PATCH] implement vertex array (vao+vbo)
---
pixelgl/vertex.go | 152 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 152 insertions(+)
diff --git a/pixelgl/vertex.go b/pixelgl/vertex.go
index d0af0ed..edde8cb 100644
--- a/pixelgl/vertex.go
+++ b/pixelgl/vertex.go
@@ -1,5 +1,7 @@
package pixelgl
+import "github.com/go-gl/gl/v3.3-core/gl"
+
// VertexFormat defines a data format in a vertex buffer.
//
// Example:
@@ -7,6 +9,15 @@ package pixelgl
// vf := VertexFormat{{Position, 2}, {Color, 4}, {TexCoord, 2}}
type VertexFormat []VertexAttribute
+// Size returns the total size of all vertex attributes in a vertex format.
+func (vf VertexFormat) Size() int {
+ size := 0
+ for _, va := range vf {
+ size += va.Size
+ }
+ return size
+}
+
// VertexAttribute specifies a single attribute in a vertex buffer.
// All vertex attributes are composed of float64s.
//
@@ -32,3 +43,144 @@ const (
TexCoord
NumStandardVertexAttrib
)
+
+// VertexUsage specifies how often the vertex array data will be updated.
+type VertexUsage int
+
+// Possible VertexUsage values are:
+// 1. StaticUsage - never or rarely updated
+// 2. DynamicUsage - often updated
+// 3. StreamUsage - updated every frame
+const (
+ StaticUsage VertexUsage = gl.STATIC_DRAW
+ DynamicUsage = gl.DYNAMIC_DRAW
+ StreamUsage = gl.STREAM_DRAW
+)
+
+// VertexDrawMode specifies how should the vertices be drawn.
+type VertexDrawMode int
+
+// Possible VertexDrawMode values are:
+// 1. PointsDrawMode - just draw individual PointsDrawMode
+// 2. LinesDrawMode - take pairs of vertices and draw a line from each pair
+// 3. LineStripDrawMode - take each two subsequent vertices and draw a line from each two
+// 4. LineLoopDrawMode - same as line strip, but also draw a line between the first and the last vertex
+// 5. TrianglesDrawMode - take triples of vertices and draw a triangle from each triple
+// 6. TriangleStripDrawMode - take each three subsequent vertices and draw a triangle from each three
+// 7. TriangleFanDrawMode - take each two subsequent vertices excluding the first vertex and draw a triangle from the first vertex and the two
+const (
+ PointsDrawMode VertexDrawMode = gl.POINTS
+ LinesDrawMode = gl.LINES
+ LineStripDrawMode = gl.LINE_STRIP
+ LineLoopDrawMode = gl.LINE_LOOP
+ TrianglesDrawMode = gl.TRIANGLES
+ TriangleStripDrawMode = gl.TRIANGLE_STRIP
+ TriangleFanDrawMode = gl.TRIANGLE_FAN
+)
+
+// VertexArray is an OpenGL vertex array object that also holds it's own vertex buffer object.
+// From the user's points of view, VertexArray is an array of vertices that can be drawn.
+type VertexArray struct {
+ parent BeginEnder
+ format VertexFormat
+ vao uint32
+ vbo uint32
+ mode VertexDrawMode
+ count int
+}
+
+// NewVertexArray creates a new vertex array and wrap another BeginEnder around it.
+func NewVertexArray(parent BeginEnder, format VertexFormat, mode VertexDrawMode, usage VertexUsage, data []float64) *VertexArray {
+ va := &VertexArray{
+ parent: parent,
+ format: format,
+ mode: mode,
+ }
+ Do(func() {
+ gl.GenVertexArrays(1, &va.vao)
+ gl.BindVertexArray(va.vao)
+
+ gl.GenBuffers(1, &va.vbo)
+ gl.BindBuffer(gl.ARRAY_BUFFER, va.vbo)
+ gl.BufferData(gl.ARRAY_BUFFER, 8*len(data), gl.Ptr(data), uint32(usage))
+
+ stride := format.Size()
+ va.count = len(data) / stride
+
+ offset := 0
+ for i, attr := range format {
+ gl.VertexAttribPointer(
+ uint32(i),
+ int32(attr.Size),
+ gl.DOUBLE,
+ false,
+ int32(stride),
+ gl.PtrOffset(8*offset),
+ )
+ gl.EnableVertexAttribArray(uint32(i))
+ offset += attr.Size
+ }
+
+ gl.BindBuffer(gl.ARRAY_BUFFER, 0)
+ gl.BindVertexArray(0)
+ })
+ return va
+}
+
+// VertexFormat returns the format of the vertices inside a vertex array.
+//
+// Do not change this format!
+func (va *VertexArray) VertexFormat() VertexFormat {
+ return va.format
+}
+
+// SetDrawMode sets the draw mode of a vertex array. Subsequent calls to Draw will use this draw mode.
+func (va *VertexArray) SetDrawMode(mode VertexDrawMode) {
+ Do(func() {
+ va.mode = mode
+ })
+}
+
+// DrawMode returns the most recently set draw mode of a vertex array.
+func (va *VertexArray) DrawMode() VertexDrawMode {
+ mode := DoVal(func() interface{} {
+ return va.mode
+ })
+ return mode.(VertexDrawMode)
+}
+
+// Draw draws a vertex array.
+func (va *VertexArray) Draw() {
+ va.Begin()
+ va.End()
+}
+
+// UpdateData overwrites the current vertex array data starting at the index offset.
+//
+// Offset is not a number of bytes, instead, it's an index in the array.
+func (va *VertexArray) UpdateData(offset int, data []float64) {
+ Do(func() {
+ gl.BindBuffer(gl.ARRAY_BUFFER, va.vbo)
+ gl.BufferSubData(gl.ARRAY_BUFFER, 8*offset, 8*len(data), gl.Ptr(data))
+ gl.BindBuffer(gl.ARRAY_BUFFER, 0)
+ })
+}
+
+// Begin binds a vertex array and it's associated vertex buffer.
+func (va *VertexArray) Begin() {
+ va.parent.Begin()
+ Do(func() {
+ gl.BindVertexArray(va.vao)
+ gl.BindBuffer(gl.ARRAY_BUFFER, va.vbo)
+ })
+}
+
+// End draws a vertex array and unbinds it alongside with it's associated vertex buffer.
+func (va *VertexArray) End() {
+ Do(func() {
+ gl.DrawArrays(uint32(va.mode), 0, int32(va.count))
+ gl.BindBuffer(gl.ARRAY_BUFFER, 0)
+ gl.BindVertexArray(0)
+ })
+ va.parent.End()
+}
--
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