mirror of
https://github.com/hajimehoshi/ebiten.git
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42 lines
1.0 KiB
Go
42 lines
1.0 KiB
Go
// Copyright 2018 The Ebiten Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package graphics
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import (
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"math"
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)
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// MipmapLevel returns an appropriate mipmap level for the given determinant of a geometry matrix.
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//
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// MipmapLevel returns -1 if det is 0.
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//
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// MipmapLevel panics if det is NaN.
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func MipmapLevel(det float32) int {
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if math.IsNaN(float64(det)) {
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panic("graphicsutil: det must be finite")
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}
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if det == 0 {
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return -1
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}
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d := math.Abs(float64(det))
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level := 0
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for d < 0.25 {
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level++
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d *= 4
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}
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return level
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}
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