forked from google/gxui
/
draw_mode.go
44 lines (38 loc) · 965 Bytes
/
draw_mode.go
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// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package gl
import (
"fmt"
"github.com/goxjs/gl"
)
type drawMode int
const (
dmPoints drawMode = gl.POINTS
dmLineStrip drawMode = gl.LINE_STRIP
dmLineLoop drawMode = gl.LINE_LOOP
dmLines drawMode = gl.LINES
dmTriangleStrip drawMode = gl.TRIANGLE_STRIP
dmTriangleFan drawMode = gl.TRIANGLE_FAN
dmTriangles drawMode = gl.TRIANGLES
)
func (d drawMode) primitiveCount(vertexCount int) int {
switch d {
case dmPoints:
return vertexCount
case dmLineStrip:
return vertexCount - 1
case dmLineLoop:
return vertexCount
case dmLines:
return vertexCount / 2
case dmTriangleStrip:
return vertexCount - 2
case dmTriangleFan:
return vertexCount - 2
case dmTriangles:
return vertexCount / 3
default:
panic(fmt.Errorf("Unknown drawMode 0x%.4x", d))
}
}