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@@ -21,9 +21,10 @@ type VBO struct {
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// VBOattrib describes one attribute of an OpenGL Vertex Buffer Object.
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type VBOattrib struct {
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- Type AttribType // Type of the attribute
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- Name string // Name of the attribute
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- ItemSize int32 // Number of elements
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+ Type AttribType // Type of the attribute
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+ Name string // Name of the attribute
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+ ItemSize int32 // Number of components
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+ ByteOffset uint32 // Byte offset from the start of the VBO
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}
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// AttribType is the functional type of a vbo attribute.
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@@ -38,13 +39,23 @@ const (
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)
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// Map from attribute type to default attribute name.
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-var attribTypeMap = map[AttribType]string{
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+var attribTypeNameMap = map[AttribType]string{
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VertexPosition: "VertexPosition",
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VertexNormal: "VertexNormal",
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VertexColor: "VertexColor",
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VertexTexcoord: "VertexTexcoord",
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}
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+// Map from attribute type to default attribute size.
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+var attribTypeSizeMap = map[AttribType]int32{
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+ VertexPosition: 3,
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+ VertexNormal: 3,
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+ VertexColor: 3,
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+ VertexTexcoord: 2,
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+}
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+
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+const floatSize = uint32(unsafe.Sizeof(float32(0)))
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+
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// NewVBO creates and returns a pointer to a new OpenGL Vertex Buffer Object.
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func NewVBO(buffer math32.ArrayF32) *VBO {
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@@ -64,24 +75,51 @@ func (vbo *VBO) init() {
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vbo.attribs = make([]VBOattrib, 0)
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}
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-// AddAttrib adds a new attribute to the VBO by attribute type.
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-func (vbo *VBO) AddAttrib(atype AttribType, itemSize int32) *VBO {
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+// AddAttrib adds a new attribute to the VBO with the specified type.
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+// The attribute's ByteOffset is computed automatically based on the existing attributes.
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+func (vbo *VBO) AddAttrib(atype AttribType) *VBO {
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+
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+ vbo.attribs = append(vbo.attribs, VBOattrib{
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+ Type: atype,
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+ Name: attribTypeNameMap[atype],
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+ ItemSize: attribTypeSizeMap[atype],
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+ ByteOffset: uint32(vbo.StrideSize()),
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+ })
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+ return vbo
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+}
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+
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+// AddAttribOffset adds a new attribute to the VBO with the specified type and byteOffset.
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+func (vbo *VBO) AddAttribOffset(atype AttribType, byteOffset uint32) *VBO {
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vbo.attribs = append(vbo.attribs, VBOattrib{
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- Type: atype,
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- Name: attribTypeMap[atype],
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- ItemSize: itemSize,
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+ Type: atype,
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+ Name: attribTypeNameMap[atype],
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+ ItemSize: attribTypeSizeMap[atype],
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+ ByteOffset: byteOffset,
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})
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return vbo
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}
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-// AddAttribName adds a new attribute to the VBO by name.
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-func (vbo *VBO) AddAttribName(name string, itemSize int32) *VBO {
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+// AddCustomAttrib adds a new attribute to the VBO with the specified name and itemSize.
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+func (vbo *VBO) AddCustomAttrib(name string, itemSize int32) *VBO {
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vbo.attribs = append(vbo.attribs, VBOattrib{
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- Type: Undefined,
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- Name: name,
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- ItemSize: itemSize,
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+ Type: Undefined,
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+ Name: name,
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+ ItemSize: itemSize,
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+ ByteOffset: uint32(vbo.StrideSize()),
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+ })
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+ return vbo
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+}
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+
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+// AddCustomAttribOffset adds a new attribute to the VBO with the specified name, itemSize and byteOffset.
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+func (vbo *VBO) AddCustomAttribOffset(name string, itemSize int32, byteOffset uint32) *VBO {
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+
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+ vbo.attribs = append(vbo.attribs, VBOattrib{
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+ Type: Undefined,
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+ Name: name,
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+ ItemSize: itemSize,
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+ ByteOffset: byteOffset,
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})
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return vbo
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}
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@@ -234,9 +272,6 @@ func (vbo *VBO) Transfer(gs *GLS) {
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// Calculates stride size
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strideSize := vbo.StrideSize()
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// For each attribute
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- var items uint32
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- var offset uint32
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- elsize := int32(unsafe.Sizeof(float32(0)))
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for _, attrib := range vbo.attribs {
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// Get attribute location in the current program
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loc := gs.prog.GetAttribLocation(attrib.Name)
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@@ -246,9 +281,7 @@ func (vbo *VBO) Transfer(gs *GLS) {
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}
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// Enables attribute and sets its stride and offset in the buffer
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gs.EnableVertexAttribArray(uint32(loc))
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- gs.VertexAttribPointer(uint32(loc), attrib.ItemSize, FLOAT, false, int32(strideSize), offset)
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- items += uint32(attrib.ItemSize)
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- offset = uint32(elsize) * items
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+ gs.VertexAttribPointer(uint32(loc), attrib.ItemSize, FLOAT, false, int32(strideSize), attrib.ByteOffset)
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}
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vbo.gs = gs // this indicates that the vbo was initialized
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}
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@@ -307,7 +340,6 @@ func (vbo *VBO) ReadVectors3(attribType AttribType, cb func(vec math32.Vector3)
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}
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}
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-
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// Read3Vectors3 iterates over all 3-float32 items (3 items at a time) for the specified attribute
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// and calls the specified callback function with the value of each of the 3 items as Vector3.
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// The callback function returns false to continue or true to break.
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@@ -331,4 +363,4 @@ func (vbo *VBO) ReadTripleVectors3(attribType AttribType, cb func(vec1, vec2, ve
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break
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}
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}
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-}
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+}
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Daniel Salvadori