59 lines
1.9 KiB
Go
59 lines
1.9 KiB
Go
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package pixel
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import "github.com/faiface/pixel/pixelgl"
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// Warning: technical stuff below.
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// VertexFormat is an internal format of the OpenGL vertex data.
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//
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// You can actually change this and all of the Pixel's functions will use the new format.
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// Only change when you're implementing an OpenGL effect or something similar.
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var VertexFormat = DefaultVertexFormat()
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// DefaultVertexFormat returns the default vertex format used by Pixel.
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func DefaultVertexFormat() pixelgl.VertexFormat {
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return pixelgl.VertexFormat{
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{Purpose: pixelgl.Position, Size: 2},
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{Purpose: pixelgl.Color, Size: 4},
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{Purpose: pixelgl.TexCoord, Size: 2},
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}
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}
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// ConvertVertexData converts data in the oldFormat to the newFormat. Vertex attributes in the new format
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// will be copied from the corresponding vertex attributes in the old format. If a vertex attribute in the new format
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// has no corresponding attribute in the old format, it will be filled with zeros.
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func ConvertVertexData(oldFormat, newFormat pixelgl.VertexFormat, data []float64) []float64 {
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// calculate the mapping between old and new format
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// if i is a start of a vertex attribute in the new format, then mapping[i] returns
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// the index where the same attribute starts in the old format
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mapping := make(map[int]int)
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i := 0
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for _, newAttr := range newFormat {
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j := 0
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for _, oldAttr := range oldFormat {
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if newAttr == oldAttr {
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mapping[i] = j
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break
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}
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j += oldAttr.Size
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}
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i += newAttr.Size
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}
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oldData, newData := data, []float64{}
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for i := 0; i < len(oldData); i += oldFormat.Size() {
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j := 0
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for _, attr := range newFormat {
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if oldIndex, ok := mapping[j]; ok { // the attribute was found in the old format
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newData = append(newData, oldData[i+oldIndex:i+oldIndex+attr.Size]...)
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} else { // the attribute wasn't found in the old format, so fill with zeros
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newData = append(newData, make([]float64, attr.Size)...)
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}
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j += attr.Size
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}
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}
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return newData
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}
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