OpenGLES3D编程技巧与优化

### OpenGL ES 3D 编程技巧与优化 #### 1. 指定材质 在 OpenGL ES 中，材质由几个属性定义，它是一种状态，会一直保持激活，直到我们再次更改或 OpenGL ES 上下文丢失。要设置当前激活的材质属性，可以使用以下代码： ```java gl.glMaterialfv(GL10.GL_FRONT_AND_BACK, GL10.GL_AMBIENT, ambientColor, 0); gl.glMaterialfv(GL10.GL_FRONT_AND_BACK, GL10.GL_DIFFUSE, diffuseColor, 0); gl.glMaterialfv(GL10.GL_FRONT_AND_BACK, GL10.GL_SPECULAR, specularColor, 0); ``` 通常，我们需要指定环境光、漫反射光和镜面反射光的 RGBA 颜色，这与指定光源属性时一样，通过四元素浮点数组来完成。将这些操作封装到一个辅助类中非常简单，以下是示例代码： ```java package com.badlogic.androidgames.framework.gl; import javax.microedition.khronos.opengles.GL10; public class Material { float[] ambient = { 0.2f, 0.2f, 0.2f, 1.0f }; float[] diffuse = { 1.0f, 1.0f, 1.0f, 1.0f }; float[] specular = { 0.0f, 0.0f, 0.0f, 1.0f }; public void setAmbient(float r, float g, float b, float a) { ambient[0] = r; ambient[1] = g; ambient[2] = b; ambient[3] = a; } public void setDiffuse(float r, float g, float b, float a) { diffuse[0] = r; diffuse[1] = g; diffuse[2] = b; diffuse[3] = a; } public void setSpecular(float r, float g, float b, float a) { specular[0] = r; specular[1] = g; specular[2] = b; specular[3] = a; } public void enable(GL10 gl) { gl.glMaterialfv(GL10.GL_FRONT_AND_BACK, GL10.GL_AMBIENT, ambient, 0); gl.glMaterialfv(GL10.GL_FRONT_AND_BACK, GL10.GL_DIFFUSE, diffuse, 0); gl.glMaterialfv(GL10.GL_FRONT_AND_BACK, GL10.GL_SPECULAR, specular, 0); } } ``` 此外，OpenGL ES 还有一种颜色材质的技巧。通过调用 `gl.glEnable(GL10.GL_COLOR_MATERIAL);`，OpenGL ES 会将模型的顶点颜色作为环境光和漫反射光的材质颜色。由于环境光和漫反射光颜色通常相同，且在大多数演示和游戏中不使用镜面高光，因此可以只启用颜色材质，而不使用 `glMaterialfv()` 调用。 #### 2. 指定法线 为了使 OpenGL ES 中的光照正常工作，我们必须为模型的每个顶点指定顶点法线。顶点法线是一个单位长度的向量，指向顶点所属表面的（平均）朝向方向。以下是一个简单的示例： ```java float[] vertices = { -0.5f, -0.5f, 0, 0, 0, 1, 0.5f, -0.5f, 0, 0, 0, 1, 0.0f, 0.5f, 0, 0, 0, 1 }; Vertices3 vertices = new Vertices3(glGraphics, 3, 0, false, false, true); vertices.setVertices(vertices); ``` 为了上传顶点法线，我们需要修改 `Vertices3` 类。以下是最终修订后的 `Vertices3` 类： ```java package com.badlogic.androidgames.framework.gl; import java.nio.ByteBuffer; import java.nio.ByteOrder; import java.nio.IntBuffer; import java.nio.ShortBuffer; import javax.microedition.khronos.opengles.GL10; import com.badlogic.androidgames.framework.impl.GLGraphics; public class Vertices3 { final GLGraphics glGraphics; final boolean hasColor; final boolean hasTexCoords; final boolean hasNormals; final int vertexSize; final IntBuffer vertices; final int[] tmpBuffer; final ShortBuffer indices; public Vertices3(GLGraphics glGraphics, int maxVertices, int maxIndices, boolean hasColor, boolean hasTexCoords, boolean hasNormals) { this.glGraphics = glGraphics; this.hasColor = hasColor; this.hasTexCoords = hasTexCoords; this.hasNormals = hasNormals; this.vertexSize = (3 + (hasColor ? 4 : 0) + (hasTexCoords ? 2 : 0) + (hasNormals ? 3 : 0)) * 4; this.tmpBuffer = new int[maxVertices * vertexSize / 4]; ByteBuffer buffer = ByteBuffer.allocateDirect(maxVertices * vertexSize); buffer.order(ByteOrder.nativeOrder()); vertices = buffer.asIntBuffer(); if (maxIndices > 0) { buffer = ByteBuffer.allocateDirect(maxIndices * Short.SIZE / 8); buffer.order(ByteOrder.nativeOrder()); indices = buffer.asShortBuffer(); } else { indices = null; } } public void setVertices(float[] vertices, int offset, int length) { this.vertices.clear(); int len = offset + length; for (int i = offset, j = 0; i < len; i++, j++) tmpBuffer[j] = Float.floatToRawIntBits(vertices[i]); this.vertices.put(tmpBuffer, 0, length); this.vertices.flip(); } public void setIndices(short[] indices, int offset, int length) { this.indices.clear(); this.indices.put(indices, offset, length); this.indices.flip(); } public void bind() { GL10 gl = glGraphics.getGL(); gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); vertices.position(0); gl.glVertexPointer(3, GL10.GL_FLOAT, vertexSize, vertices); if (hasColor) { gl.glEnableClientState(GL10.GL_COLOR_ARRAY); vertices.position(3); gl.glColorPointer(4, GL10.GL_FLOAT, vertexSize, vertices); } if (hasTexCoords) { gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY); vertices.position(hasColor ? 7 : 3); gl.glTexCoordPointer(2, GL10.GL_FLOAT, vertexSize, vertices); } if (hasNormals) { gl.glEnableClientState(GL10.GL_NORMAL_ARRAY); int offset = 3; if (hasColor) offset += 4; if (hasTexCoords) offset += 2; vertices.position(offset); gl.glNormalPointer(GL10.GL_FLOAT, vertexSize, vertices); } } public void draw(int primitiveType, int offset, int numVertices) { GL10 gl = glGraphics.getGL(); if (indices != null) { indices.position(offset); gl.glDrawElements(primitiveType, numVertices, GL10.GL_UNSIGNED_SHORT, indices); } else { gl.glDrawArrays(primitiveType, offset, numVertices); } } public void unbind() { GL10 gl = glGraphics.getGL(); if (hasTexCoords) gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY); if (hasColor) gl.glDisableClientState(GL10.GL_COLOR_ARRAY); if (hasNormals) gl.glDisableClientState(GL10.GL_NORMAL_ARRAY); } } ``` 这个类的修改主要包括添加了 `hasNormals` 布尔值来跟踪顶点是否有法线，修改了 `vertexSize` 的计算，以及在 `bind()` 方法中添加了对法线的处理。 #### 3. 综合应用：光照场景示例 以下是一个综合示例，展示了如何使用上述技巧创建一个包含全局环