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/*
* Copyright (C) 2019 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package android.gameperformance;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
/**
* Helper class that generates patch to render. Patch is a regular polygon with the center in 0.
* Regular polygon fits in circle with requested radius.
*/
public class RenderPatch {
public static final int FLOAT_SIZE = 4;
public static final int SHORT_SIZE = 2;
public static final int VERTEX_COORD_COUNT = 3;
public static final int VERTEX_STRIDE = VERTEX_COORD_COUNT * FLOAT_SIZE;
public static final int TEXTURE_COORD_COUNT = 2;
public static final int TEXTURE_STRIDE = TEXTURE_COORD_COUNT * FLOAT_SIZE;
// Tessellation is done using points on circle.
public static final int TESSELLATION_BASE = 0;
// Tesselation is done using extra point in 0.
public static final int TESSELLATION_TO_CENTER = 1;
// Radius of circle that fits polygon.
private final float mDimension;
private final ByteBuffer mVertexBuffer;
private final ByteBuffer mTextureBuffer;
private final ByteBuffer mIndexBuffer;
public RenderPatch(int triangleCount, float dimension, int tessellation) {
mDimension = dimension;
int pointCount;
int externalPointCount;
if (triangleCount < 1) {
throw new IllegalArgumentException("Too few triangles to perform tessellation");
}
switch (tessellation) {
case TESSELLATION_BASE:
externalPointCount = triangleCount + 2;
pointCount = externalPointCount;
break;
case TESSELLATION_TO_CENTER:
if (triangleCount < 3) {
throw new IllegalArgumentException(
"Too few triangles to perform tessellation to center");
}
externalPointCount = triangleCount;
pointCount = triangleCount + 1;
break;
default:
throw new IllegalArgumentException("Wrong tesselation requested");
}
if (pointCount > Short.MAX_VALUE) {
throw new IllegalArgumentException("Number of requested triangles is too big");
}
mVertexBuffer = ByteBuffer.allocateDirect(pointCount * VERTEX_STRIDE);
mVertexBuffer.order(ByteOrder.nativeOrder());
mTextureBuffer = ByteBuffer.allocateDirect(pointCount * TEXTURE_STRIDE);
mTextureBuffer.order(ByteOrder.nativeOrder());
for (int i = 0; i < externalPointCount; ++i) {
// Use 45 degree rotation to make quad aligned along axises in case
// triangleCount is four.
final double angle = Math.PI * 0.25 + (Math.PI * 2.0 * i) / (externalPointCount);
// Positions
mVertexBuffer.putFloat((float) (dimension * Math.sin(angle)));
mVertexBuffer.putFloat((float) (dimension * Math.cos(angle)));
mVertexBuffer.putFloat(0.0f);
// Texture coordinates.
mTextureBuffer.putFloat((float) (0.5 + 0.5 * Math.sin(angle)));
mTextureBuffer.putFloat((float) (0.5 - 0.5 * Math.cos(angle)));
}
if (tessellation == TESSELLATION_TO_CENTER) {
// Add center point.
mVertexBuffer.putFloat(0.0f);
mVertexBuffer.putFloat(0.0f);
mVertexBuffer.putFloat(0.0f);
mTextureBuffer.putFloat(0.5f);
mTextureBuffer.putFloat(0.5f);
}
mIndexBuffer =
ByteBuffer.allocateDirect(
triangleCount * 3 /* indices per triangle */ * SHORT_SIZE);
mIndexBuffer.order(ByteOrder.nativeOrder());
switch (tessellation) {
case TESSELLATION_BASE:
for (int i = 0; i < triangleCount; ++i) {
mIndexBuffer.putShort((short) 0);
mIndexBuffer.putShort((short) (i + 1));
mIndexBuffer.putShort((short) (i + 2));
}
break;
case TESSELLATION_TO_CENTER:
for (int i = 0; i < triangleCount; ++i) {
mIndexBuffer.putShort((short)i);
mIndexBuffer.putShort((short)((i + 1) % externalPointCount));
mIndexBuffer.putShort((short)externalPointCount);
}
break;
}
if (mVertexBuffer.remaining() != 0 || mTextureBuffer.remaining() != 0 || mIndexBuffer.remaining() != 0) {
throw new RuntimeException("Failed to fill buffers");
}
mVertexBuffer.position(0);
mTextureBuffer.position(0);
mIndexBuffer.position(0);
}
public float getDimension() {
return mDimension;
}
public ByteBuffer getVertexBuffer() {
return mVertexBuffer;
}
public ByteBuffer getTextureBuffer() {
return mTextureBuffer;
}
public ByteBuffer getIndexBuffer() {
return mIndexBuffer;
}
}
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