我正在尝试从浮点数组缓冲区中的OpenGL ES 2.0中逐点绘制顶点位置和颜色，但是每次绘制只能接受4个顶点。当我添加更多然后告诉它绘制更多时，它只会在数组中绘制2个不相邻的顶点。为什么会这样呢？为什么在一个实例中不能绘制四个以上的顶点？如果可以的话，怎么办？
这是一个例子。
当我拥有3*4数组数据时，它会像这样绘制它们：
. . . .，已正确完成。
例如，如果我设置3*6数组数据，则它不会绘制6点，它会绘制如下图所示：
. .
我的大部分代码来自OpenGL ES课程项目，我仍在学习，并且不太了解onSurfaceCreated中的事情是如何完成的。
这是我的OpenGLRenderer类：
@Override
public void onSurfaceCreated(GL10 gl, EGLConfig config) {
...
final String vertexShader =
"uniform mat4 u_MVPMatrix; \n" // A constant representing the combined model/view/projection matrix.
+ "attribute vec4 a_Position; \n" // Per-vertex position information we will pass in.
+ "attribute vec4 a_Color; \n" // Per-vertex color information we will pass in.
+ "varying vec4 v_Color; \n" // This will be passed into the fragment shader.
+ "void main() \n" // The entry point for our vertex shader.
+ "{ \n"
+ " v_Color = a_Color; \n" // Pass the color through to the fragment shader.
// It will be interpolated across the triangle.
+ " gl_Position = u_MVPMatrix \n" // gl_Position is a special variable used to store the final position.
+ " * a_Position; \n" // Multiply the vertex by the matrix to get the final point in
+ "} \n"; // normalized screen coordinates.
final String fragmentShader =
"precision mediump float; \n" // Set the default precision to medium. We don't need as high of a
// precision in the fragment shader.
+ "varying vec4 v_Color; \n" // This is the color from the vertex shader interpolated across the
// triangle per fragment.
+ "void main() \n" // The entry point for our fragment shader.
+ "{ \n"
+ " gl_FragColor = v_Color; \n" // Pass the color directly through the pipeline.
+ "} \n";
// Load in the vertex shader.
int vertexShaderHandle = GLES20.glCreateShader(GLES20.GL_VERTEX_SHADER);
if (vertexShaderHandle != 0)
{
// Pass in the shader source.
GLES20.glShaderSource(vertexShaderHandle, vertexShader);
// Compile the shader.
GLES20.glCompileShader(vertexShaderHandle);
// Get the compilation status.
final int[] compileStatus = new int[1];
GLES20.glGetShaderiv(vertexShaderHandle, GLES20.GL_COMPILE_STATUS, compileStatus, 0);
// If the compilation failed, delete the shader.
if (compileStatus[0] == 0)
{
GLES20.glDeleteShader(vertexShaderHandle);
vertexShaderHandle = 0;
}
}
if (vertexShaderHandle == 0)
{
throw new RuntimeException("Error creating vertex shader.");
}
// Load in the fragment shader shader.
int fragmentShaderHandle = GLES20.glCreateShader(GLES20.GL_FRAGMENT_SHADER);
if (fragmentShaderHandle != 0)
{
// Pass in the shader source.
GLES20.glShaderSource(fragmentShaderHandle, fragmentShader);
// Compile the shader.
GLES20.glCompileShader(fragmentShaderHandle);
// Get the compilation status.
final int[] compileStatus = new int[1];
GLES20.glGetShaderiv(fragmentShaderHandle, GLES20.GL_COMPILE_STATUS, compileStatus, 0);
// If the compilation failed, delete the shader.
if (compileStatus[0] == 0)
{
GLES20.glDeleteShader(fragmentShaderHandle);
fragmentShaderHandle = 0;
}
}
if (fragmentShaderHandle == 0)
{
throw new RuntimeException("Error creating fragment shader.");
}
// Create a program object and store the handle to it.
int programHandle = GLES20.glCreateProgram();
if (programHandle != 0)
{
// Bind the vertex shader to the program.
GLES20.glAttachShader(programHandle, vertexShaderHandle);
// Bind the fragment shader to the program.
GLES20.glAttachShader(programHandle, fragmentShaderHandle);
// Bind attributes
GLES20.glBindAttribLocation(programHandle, 0, "a_Position");
GLES20.glBindAttribLocation(programHandle, 1, "a_Color");
// Link the two shaders together into a program.
GLES20.glLinkProgram(programHandle);
// Get the link status.
final int[] linkStatus = new int[1];
GLES20.glGetProgramiv(programHandle, GLES20.GL_LINK_STATUS, linkStatus, 0);
// If the link failed, delete the program.
if (linkStatus[0] == 0)
{
GLES20.glDeleteProgram(programHandle);
programHandle = 0;
}
}
if (programHandle == 0)
{
throw new RuntimeException("Error creating program.");
}
// Set program handles. These will later be used to pass in values to the program.
mMVPMatrixHandle = GLES20.glGetUniformLocation(programHandle, "u_MVPMatrix");
mPositionHandle = GLES20.glGetAttribLocation(programHandle, "a_Position");
mColorHandle = GLES20.glGetAttribLocation(programHandle, "a_Color");
// Tell OpenGL to use this program when rendering.
GLES20.glUseProgram(programHandle);
}
画点：
@Override
public void onDrawFrame(GL10 gl) {
GLES20.glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
GLES20.glClear(GLES20.GL_DEPTH_BUFFER_BIT | GLES20.GL_COLOR_BUFFER_BIT);
Matrix.setIdentityM(mModelMatrix, 0);
drawPoints();
}
// Like I said, 4 and below works without any issue
private final int vertexesToDraw = 6;
// x, y, z (z being upwards)
private final float[] vertexPosData = {
0.0f, 0.0f, 0.0f,
1.0f, 0.0f, 0.0f,
2.0f, 0.0f, 0.0f,
3.0f, 0.0f, 0.0f,
4.0f, 0.0f, 0.0f,
5.0f, 0.0f, 0.0f
};
// red, green, blue, alpha
private final float[] vertexColorData = {
1.0f, 0.0f, 0.0f, 1.0f,
0.0f, 1.0f, 0.0f, 1.0f,
0.0f, 0.0f, 1.0f, 1.0f,
1.0f, 0.0f, 0.0f, 1.0f,
0.0f, 1.0f, 0.0f, 1.0f,
0.0f, 0.0f, 1.0f, 1.0f
};
FloatBuffer mVertexPos, mVertexColor;
// this gets initialized first
private void setupPoints() {
mVertexPos = ByteBuffer.allocateDirect(vertexPosData.length * 4).order(ByteOrder.nativeOrder()).asFloatBuffer();
mVertexPos.put(vertexPosData).position(0);
mVertexPos.position(0);
mVertexColor = ByteBuffer.allocateDirect(vertexColorData.length * 4).order(ByteOrder.nativeOrder()).asFloatBuffer();
mVertexColor.put(vertexColorData).position(0);
mVertexColor.position(0);
}
private void drawPoints() {
GLES20.glVertexAttribPointer(mPositionHandle, 3, GLES20.GL_FLOAT, false, 3 * vertexesToDraw, mVertexPos);
GLES20.glEnableVertexAttribArray(mPositionHandle);
GLES20.glVertexAttribPointer(mColorHandle, 4, GLES20.GL_FLOAT, false, 4 * vertexesToDraw, mVertexColor);
GLES20.glEnableVertexAttribArray(mColorHandle);
Matrix.multiplyMM(mMVPMatrix, 0, mViewMatrix, 0, mModelMatrix, 0);
Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mMVPMatrix, 0);
GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mMVPMatrix, 0);
GLES20.glDrawArrays(GLES20.GL_POINTS, 0, vertexesToDraw);
}
答案 0 :(得分：2)
glVertexAttribPointer的第五个参数是连续通用顶点属性（stride）之间的字节偏移，而不是缓冲区中元素的数量。
这意味着，对于float类型的属性（float的大小为4个字节）并且元组大小为3（例如x，y，z坐标），跨度参数必须为4 * 3 = 12。 br /> 对于元组大小为4（RGBA颜色）的属性，步幅参数必须为4 * 4 = 16。
GLES20.glVertexAttribPointer(mPositionHandle, 3, GLES20.GL_FLOAT, false, 3 * 4, mVertexPos);
GLES20.glEnableVertexAttribArray(mPositionHandle);
GLES20.glVertexAttribPointer(mColorHandle, 4, GLES20.GL_FLOAT, false, 4 * 4, mVertexColor);
GLES20.glEnableVertexAttribArray(mColorHandle);
由于顶点紧密堆积，因此可以将 stride 设置为0。这是glVertexAttribPointer提供的一种特殊情况。当 stride 为0时，它将由 size 和 type 参数自动计算。
GLES20.glVertexAttribPointer(mPositionHandle, 3, GLES20.GL_FLOAT, false, 0, mVertexPos);
GLES20.glEnableVertexAttribArray(mPositionHandle);
GLES20.glVertexAttribPointer(mColorHandle, 4, GLES20.GL_FLOAT, false, 0, mVertexColor);
GLES20.glEnableVertexAttribArray(mColorHandle);
请注意，当您有4个属性时，缓冲区中的元素数（浮点值的数量）恰好匹配连续通用顶点属性之间的字节偏移。因此4个顶点可以同时工作，但6个顶点会失败。
缓冲区的大小永远不会明确设置。调用glDrawArrays时，启用的顶点属性必须引用一个缓冲区，该缓冲区足够大以提供所需的属性。