glMapBufferRange（）返回使用TrasnformFeedback的Android 3.0 OpenGLES全部为零 [英] glMapBufferRange() returns all zeros in Android OpenGLES 3.0 using TrasnformFeedback
问题描述
更新：这是工作，最多在要点吧！由于雷托
UPDATE: This is working and up on gist now! Thanks Reto
我的工作在Android实现变换反馈如下这个例子的。运行pretty也没有任何错误，但阅读与 glMapBufferRange的TransformFeedback缓冲（）时，我得到全零退出
I am working on an Android implementation of transform feedback following this example. runs pretty well without any errors, but I am getting all zeros out when reading the TransformFeedback buffer with glMapBufferRange()
import android.opengl.GLES30;
import android.util.Log;
import java.nio.ByteBuffer;
import java.nio.FloatBuffer;
/**
* Created by izzy on 6/24/15.
*/
public class TransformFeedback {
private final String TAG = "TransformFeedback";
// Vertex shader
private final String vertexShaderSrc =
"#version 300 es \n" +
"in float inValue;\n" +
"out float outValue;\n" +
"void main() {\n" +
" outValue = sqrt(inValue);\n" +
"}";
private final String fragmentShaderCode =
"#version 300 es \n" +
"precision mediump float;\n" +
"in float outValue;\n" +
"out vec4 fragColor;\n" +
"void main() {\n" +
" fragColor = vec4(outValue,outValue,outValue,1.0);\n" +
"}";
private final int mProgram;
public TransformFeedback(){
// Compile shader
int vertexShader = MyGLRenderer.loadShader(GLES30.GL_VERTEX_SHADER,
vertexShaderSrc);
int fragmentShader = MyGLRenderer.loadShader(GLES30.GL_FRAGMENT_SHADER,
fragmentShaderCode);
// Create program and specify transform feedback variables
mProgram = GLES30.glCreateProgram();
GLES30.glAttachShader(mProgram, vertexShader);
GLES30.glAttachShader(mProgram, fragmentShader);
final String[] feedbackVaryings = { "outValue" };
GLES30.glTransformFeedbackVaryings(mProgram, feedbackVaryings, GLES30.GL_INTERLEAVED_ATTRIBS);
MyGLRenderer.checkGlError("glTransformFeedbackVaryings");
GLES30.glLinkProgram(mProgram);
int[] linkSuccessful = new int[1];
GLES30.glGetProgramiv(mProgram, GLES30.GL_LINK_STATUS, linkSuccessful, 0);
if (linkSuccessful[0] != 1){
Log.d(TAG, "glLinkProgram failed");
}
MyGLRenderer.checkGlError(TAG + "glLinkProgram");
GLES30.glUseProgram(mProgram);
MyGLRenderer.checkGlError(TAG + "glUseProgram");
// Create VAO
int[] vao = new int[1];
GLES30.glGenVertexArrays(1, vao, 0);
GLES30.glBindVertexArray(vao[0]);
MyGLRenderer.checkGlError(TAG + "glBindVertexArray");
// Create input VBO and vertex format
int bufferLength = 5 * 4; //5 floats 4 bytes each
ByteBuffer bb = ByteBuffer.allocateDirect(bufferLength);
FloatBuffer data = bb.asFloatBuffer();
float[] floatData = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f };
data.put(floatData);
data.position(0);
int[] vbo = new int[1];
GLES30.glGenBuffers(1, vbo, 0);
GLES30.glBindBuffer(GLES30.GL_ARRAY_BUFFER, vbo[0]);
GLES30.glBufferData(GLES30.GL_ARRAY_BUFFER, bufferLength, data, GLES30.GL_STATIC_DRAW);
MyGLRenderer.checkGlError(TAG + "glBufferDatar");
int inputAttrib = GLES30.glGetAttribLocation(mProgram, "inValue");
GLES30.glEnableVertexAttribArray(inputAttrib);
GLES30.glVertexAttribPointer(inputAttrib, 1, GLES30.GL_FLOAT, false, 0, 0);
MyGLRenderer.checkGlError(TAG + "glVertexAttribPointer");
// Create transform feedback buffer
int[] tbo = new int[1];
GLES30.glGenBuffers(1, tbo, 0);
GLES30.glBindBuffer(GLES30.GL_ARRAY_BUFFER, tbo[0]);
GLES30.glBufferData(GLES30.GL_ARRAY_BUFFER, bufferLength, null, GLES30.GL_STATIC_READ);
// Perform feedback transform
GLES30.glEnable(GLES30.GL_RASTERIZER_DISCARD);
GLES30.glBindBufferBase(GLES30.GL_TRANSFORM_FEEDBACK_BUFFER, 0, tbo[0]);
MyGLRenderer.checkGlError(TAG + "glBindBufferBase");
GLES30.glBeginTransformFeedback(GLES30.GL_POINTS);
GLES30.glDrawArrays(GLES30.GL_POINTS, 0, 5);
GLES30.glEndTransformFeedback();
GLES30.glDisable(GLES30.GL_RASTERIZER_DISCARD);
GLES30.glFlush();
MyGLRenderer.checkGlError(TAG + "pre glMapBufferRange ");
// Fetch and print results
FloatBuffer transformedBuffer = ((ByteBuffer) GLES30.glMapBufferRange(GLES30.GL_TRANSFORM_FEEDBACK_BUFFER,
0, bufferLength, GLES30.GL_MAP_READ_BIT)).asFloatBuffer();
MyGLRenderer.checkGlError(TAG + "glMapBufferRange");
transformedBuffer.position(0);
Log.d(TAG, String.format("%f %f %f %f %f\n", transformedBuffer.get(),
transformedBuffer.get(), transformedBuffer.get(), transformedBuffer.get(), transformedBuffer.get()));
transformedBuffer.position(0);
}
}
在logcat的输出是这样的：
The logcat output looks like this:
D/TransformFeedback﹕ 0.000000 0.000000 0.000000 0.000000 0.000000
根据
<一href=\"http://stackoverflow.com/questions/29921348/safe-usage-of-glmapbufferrange-on-android-java\">this问题你可投返回的缓冲区到ByteBuffer的，所以我不相信铸造的问题。即使数据出来后向它不应该是全部为零，如果着色器code为计算正确转换反馈变量，而我贯通正确转换的反馈。
according to this question you may cast the returned buffer to a bytebuffer, so I do not believe the casting is the problem. Even if the data is coming out backwards it shouldn't be all zeros if the shader code is computing the transform feedback variable correctly, and I am linking the transform feedback correctly.
推荐答案
想通了，这要感谢雷托在此<一个href=\"http://stackoverflow.com/questions/31123376/glmapbufferrange-returning-all-zeros-in-android/31127695#31127695\">question.输出实际上是不为零。他们是反向字节顺序，即4.6006E-41彩车。简单地映射缓冲区设置为本土秩序和whallah！
Figured it out, thanks to Reto on this question. The outputs are actually not zeros. They are floats in reversed byte order, i.e. 4.6006E-41. Simply set the mapped buffer to native order and whallah!
ByteBuffer bb = ((ByteBuffer) mappedBuffer);
bb.order(ByteOrder.nativeOrder());
FloatBuffer transformedData = bb.asFloatBuffer();
Log.d(TAG, String.format("output values = %f %f %f %f %f\n", transformedData.get(),
transformedData.get(), transformedData.get(),
transformedData.get(), transformedData.get()));
完整的工作code是高达上要点
这篇关于glMapBufferRange（）返回使用TrasnformFeedback的Android 3.0 OpenGLES全部为零的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
