使用glDrawArrays绘制OpenGL ES的立方体

以前，我一直在使用glDrawElements绘制一些3D形状，但是当涉及到以不同方式着色面部时，事实证明最好拥有唯一的顶点。使用glDrawArrays绘制OpenGL ES的立方体

我一直在试图重写我以前工作的多维数据集类，以使用glDrawArrays来代替并为每个顶点提供颜色（和正常但我没有使用它）数据，但现在我无法在屏幕上看到任何东西。流程非常多：编译着色器，创建程序和附加着色器，为模型数据创建缓冲区，设置程序，传递指向模型数据的指针，传递MVP矩阵，绘制。

我认为我已经完成了我为glDrawElements所做的等价事情，所以我认为我会责怪我的着色器代码，但是我真的不清楚什么是错的。任何帮助赞赏。

public class Cube { 

private final String vertexShaderCode = 
     "uniform mat4 uMVPMatrix;" + 
     "attribute vec4 aPosition;" + 
     "attribute vec4 aColor; \n" 
     + "attribute vec3 aNormal; \n" 
     + "varying vec4 v_Color; \n"  
     + "void main() {" + 
     " gl_Position = uMVPMatrix * vPosition;" + 
     "}"; 

private final String fragmentShaderCode = 
     "precision mediump float;" + 
     "varying vec4 v_Color;" + 
     "void main() {" + 
     " gl_FragColor = v_Color;" + 
     "}"; 

// Store our data in float buffer. 
private final FloatBuffer mCubePositions; 
private final FloatBuffer mCubeColors; 
private final FloatBuffer mCubeNormals; 

// Bytes per float. 
private final int mBytesPerFloat = 4; 

/** Size of the position data in elements. */ 
private final int mPositionDataSize = 3;  
/** Size of the color data in elements. */ 
private final int mColorDataSize = 4; 
/** Size of the normal data in elements. */ 
private final int mNormalDataSize = 3; 

private final int mProgram; 
private int mPositionHandle; 
private int mColorHandle; 
private int mNormalHandle; 
private int mMVPMatrixHandle; 

final float[] cubePositionData = 
    {... 
    }; 

    final float[] cubeColorData = 
    {... 
    }; 

    final float[] cubeNormalData = 
    {... 
    }; 

/** 
* Sets up the drawing object data for use in an OpenGL ES context. 
*/ 
public Cube() { 
    // prepare shaders and OpenGL program 
    int vertexShader = MyGLRenderer.loadShader(
      GLES20.GL_VERTEX_SHADER, 
      vertexShaderCode); 
    int fragmentShader = MyGLRenderer.loadShader(
      GLES20.GL_FRAGMENT_SHADER, 
      fragmentShaderCode); 

    mProgram = GLES20.glCreateProgram();    // create empty OpenGL Program 
    GLES20.glAttachShader(mProgram, vertexShader); // add the vertex shader to program 
    GLES20.glAttachShader(mProgram, fragmentShader); // add the fragment shader to program 
    GLES20.glLinkProgram(mProgram);     // create OpenGL program executables 

    // Initialize the buffers. 
    mCubePositions = ByteBuffer.allocateDirect(cubePositionData.length * mBytesPerFloat) 
    .order(ByteOrder.nativeOrder()).asFloatBuffer();  
    mCubePositions.put(cubePositionData); 
    mCubePositions.position(0); 

    mCubeColors = ByteBuffer.allocateDirect(cubeColorData.length * mBytesPerFloat) 
    .order(ByteOrder.nativeOrder()).asFloatBuffer();  
    mCubeColors.put(cubeColorData); 
    mCubeColors.position(0); 

    mCubeNormals = ByteBuffer.allocateDirect(cubeNormalData.length * mBytesPerFloat) 
    .order(ByteOrder.nativeOrder()).asFloatBuffer();  
    mCubeNormals.put(cubeNormalData); 
    mCubeNormals.position(0); 
} 

public void draw(float[] mMVPMatrix) { 
    // Add program to OpenGL environment 
    GLES20.glUseProgram(mProgram); 

    // get handle to vertex shader's vPosition member 
    mPositionHandle = GLES20.glGetAttribLocation(mProgram, "aPosition"); 

    // get handle to vertex shader's aColor member 
    mColorHandle = GLES20.glGetAttribLocation(mProgram, "aColor"); 

    mNormalHandle = GLES20.glGetAttribLocation(mProgram, "aNormal"); 

    // get handle to shape's transformation matrix 
    mMVPMatrixHandle = GLES20.glGetUniformLocation(mProgram, "uMVPMatrix"); 

    // Apply the projection and view transformation 
    GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mMVPMatrix, 0); 

    // Pass in the position information 
    mCubePositions.position(0); 
    GLES20.glVertexAttribPointer(mPositionHandle, mPositionDataSize, 
      GLES20.GL_FLOAT, false, 0, mCubePositions); 
    GLES20.glEnableVertexAttribArray(mPositionHandle); 

    // Pass in the color information 
    mCubeColors.position(0); 
    GLES20.glVertexAttribPointer(mColorHandle, mColorDataSize, 
      GLES20.GL_FLOAT, false, 0, mCubeColors); 
    GLES20.glEnableVertexAttribArray(mColorHandle); 

    // Pass in the normal information 
    mCubeNormals.position(0); 
    GLES20.glVertexAttribPointer(mNormalHandle, mNormalDataSize, 
      GLES20.GL_FLOAT, false, 0, mCubeNormals); 
    GLES20.glEnableVertexAttribArray(mNormalHandle); 

    // Pass in the combined matrix. 
    GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mMVPMatrix, 0); 

    // Draw the cube. 
    GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, 36); 

    // Disable vertex array 
    GLES20.glDisableVertexAttribArray(mPositionHandle);  
}

来源

2014-09-18 TheLastBert

你的顶点着色器代码偏出分配一个值到v_Color不同变量，这导致没有颜色被传递从顶点着色器到片段着色器。你需要在这个顶点着色器代码添加到main()功能：

v_Color = aColor;

还有是不匹配的名字aPosition声明之间，然后使用名为vPosition一（不确定）变量。

我强烈建议您检查着色器编译的结果，并在失败时研究错误。 glGetShaderiv()和glGetShaderInfoLog()是你的朋友。

来源

2014-09-19 05:33:36

使用glDrawArrays绘制OpenGL ES的立方体

回答

相关问题