java - 如何从 OpenGL ES 2.0 中的数组中读取 4 个以上的顶点数据?
问题描述
我试图从浮点数组缓冲区中为顶点位置和颜色绘制一个相邻的点OpenGL ES 2.0
,但每次绘制只能接受 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?为什么我不能在一个实例中绘制超过 4 个顶点?如果可以,怎么做?
这是一个例子。当我有3*4
数组数据时,它会像这样绘制它们:
. . . .
,这是正确完成的。
例如,如果我设置3*6
数组数据,它不会绘制 6 个点,它会绘制如下内容:
. .
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像 in 这样的事情是如何onSurfaceCreated
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);
}
绘制点:
@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);
}
解决方案
的第 5 个参数glVertexAttribPointer
是连续通用顶点属性 ( stride
) 之间的字节偏移量,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),stride 参数必须为 4 * 3 = 12。
对于具有元组大小为 4(RGBA 颜色),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);
由于顶点紧密排列,因此可以将步幅设置为 0。这是由 提供的特殊情况glVertexAttribPointer
。当stride为 0 时,则由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,缓冲区中的元素数量(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量。所以 4 个顶点巧合工作,但 6 个顶点失败。
缓冲区的大小从不明确设置。调用时glDrawArrays
,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。
推荐阅读
- python - 不同的嵌入文档
- ruby-on-rails - 为什么我的路线给了我错误的方向
- reactjs - react-admin:如何在 Datagrid 的每一行上显示删除按钮
- python - TypeError:“NoneType”对象不可调用-Beautifulsoup 4
- c - 从内核空间声明一个指向用户空间数组的指针并填充它
- python - 如何在具有 32 位和 64 位版本的同时在虚拟环境(.virtualenvs)中安装 64 位软件包?
- java - 分隔测试文件夹的约定
- python - 如何在 Python 中使用 importlib 使用 from x import y
- vba - 我想创建一个新产品,然后在两个小时后将另一个文档中的一些部件添加到新的 ProductDoc 中,这似乎是不可能的
- javascript - 如何在axios中使用电子打印功能