add vertex format primitives

pixelgl/vertex.go

@@ -0,0 +1,34 @@
+package pixelgl
+
+// VertexFormat defines a data format in a vertex buffer.
+//
+// Example:
+//
+//   vf := VertexFormat{{Position, 2}, {Color, 4}, {TexCoord, 2}}
+type VertexFormat []VertexAttribute
+
+// VertexAttribute specifies a single attribute in a vertex buffer.
+// All vertex attributes are composed of float64s.
+//
+// A vertex attribute has a Purpose (such as Position, Color, etc.) and Size. Size specifies
+// the number of float64s the vertex attribute is composed of.
+type VertexAttribute struct {
+	Purpose VertexAttributePurpose
+	Size    int
+}
+
+// VertexAttributePurpose clarifies the purpose of a vertex attribute. This can be a color, position, texture
+// coordinates or anything else.
+//
+// VertexAttributePurpose may be used to correctly assign data to a vertex buffer.
+type VertexAttributePurpose int
+
+// Position, Color and TexCoord are the standard vertex attributes.
+//
+// Feel free to define more vertex attribute purposes (e.g. in an effects library).
+const (
+	Position VertexAttributePurpose = iota
+	Color
+	TexCoord
+	NumStandardVertexAttrib
+)