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hpp/TransformFeedback.java

Last active August 22, 2020 07:25
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  1. hpp revised this gist Jun 30, 2015. 1 changed file with 7 additions and 8 deletions.
    15 changes: 7 additions & 8 deletions TransformFeedback.java
    View file
    Original file line number Diff line number Diff line change
    @@ -135,18 +135,17 @@ public TransformFeedback(){
    // Map the transform feedback buffer to local address space.
    Buffer mappedBuffer = GLES30.glMapBufferRange(GLES30.GL_TRANSFORM_FEEDBACK_BUFFER,
    0, bufferLength, GLES30.GL_MAP_READ_BIT);
    MyGLRenderer.checkGlError(TAG + " glMapBufferRange");

    // Read out the data, here we write to logcat.
    if (mappedBuffer!=null){
    ByteBuffer transformedBuffer = ((ByteBuffer) mappedBuffer);
    transformedBuffer.order(ByteOrder.LITTLE_ENDIAN);
    MyGLRenderer.checkGlError(TAG + " glMapBufferRange");

    Log.d(TAG, String.format("output values = %f %f %f %f %f\n", transformedBuffer.getFloat(),
    transformedBuffer.getFloat(), transformedBuffer.getFloat(),
    transformedBuffer.getFloat(), transformedBuffer.getFloat()));
    transformedBuffer.position(0);
    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()));
    }
    // Don't forget to Unmap the Transform Feeback Buffer.
    GLES30.glUnmapBuffer(GLES30.GL_TRANSFORM_FEEDBACK_BUFFER);
  2. hpp created this gist Jun 30, 2015.
    154 changes: 154 additions & 0 deletions TransformFeedback.java
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,154 @@
    import android.opengl.GLES30;
    import android.util.Log;

    import java.nio.Buffer;
    import java.nio.ByteBuffer;
    import java.nio.ByteOrder;
    import java.nio.FloatBuffer;

    /**
    * Created by izzy on 6/24/15. TransformFeedback is a example of how
    * to do transform feedback on Android using OpenGLES 3.0. Closely
    * follows the example found at https://open.gl/feedback.
    *
    * Assumes you have a working instance of GLSurfaceVew. Remember to call
    * setEGLContextClientVersion(3) to set the OpenGLES context to API 3.0
    * and have the appropriate OpenGLES specified in the Android manifest file.
    */
    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" +
    "}";

    // Need a fragmentShader or glLinkProgram will throw
    private final String fragmentShaderCode =
    "#version 300 es \n" +
    "precision mediump float;\n" +
    "out vec4 fragColor;\n" +
    "void main() {\n" +
    " fragColor = vec4(1.0,1.0,1.0,1.0);\n" +
    "}";

    private final int mProgram;

    /**
    * The TransformFeedback constructor contains all the code to initialize
    * and draw the TransformFeedback, so create an instance of TransformFeedback
    * i.e. 'new TransformFeedBack()' in your 'GLRenderer.OnDrawFrame()' method.
    */
    public TransformFeedback(){

    // Compile shaders
    int vertexShader = MyGLRenderer.loadShader(GLES30.GL_VERTEX_SHADER,
    vertexShaderSrc);
    int fragmentShader = MyGLRenderer.loadShader(GLES30.GL_FRAGMENT_SHADER,
    fragmentShaderCode);

    // Create program and attach shaders
    mProgram = GLES30.glCreateProgram();
    GLES30.glAttachShader(mProgram, vertexShader);
    GLES30.glAttachShader(mProgram, fragmentShader);

    // Tell GL where the feedbackVaryings are in the shader before Linking
    // the shaders together to form a program.
    final String[] feedbackVaryings = { "outValue" };
    GLES30.glTransformFeedbackVaryings(mProgram, feedbackVaryings, GLES30.GL_INTERLEAVED_ATTRIBS);
    MyGLRenderer.checkGlError(TAG + " glTransformFeedbackVaryings");

    // Link program and look for errors
    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");

    /***********
    * Begin Rendering process
    * everything before this can be moved to an initialization stage
    ***********/

    // Bring the program into use
    GLES30.glUseProgram(mProgram);
    MyGLRenderer.checkGlError(TAG + " glUseProgram");


    // Create data to fill VBO
    int bufferLength = 5 * 4; //5 floats 4 bytes each
    FloatBuffer data = ByteBuffer.allocateDirect(bufferLength)
    .order(ByteOrder.nativeOrder()).asFloatBuffer();
    float[] floatData = { 1.0f, 4.0f, 9.0f, 16.0f, 25.0f };
    data.put(floatData).position(0);

    // Create VBO and fill with data
    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_READ);
    MyGLRenderer.checkGlError(TAG + " glBufferData GL_ARRAY_BUFFER");

    // Link created VBO to shader attribute "inValue"
    int inputAttrib = GLES30.glGetAttribLocation(mProgram, "inValue");
    GLES30.glEnableVertexAttribArray(inputAttrib);
    GLES30.glVertexAttribPointer(inputAttrib, 1, GLES30.GL_FLOAT, false, 4, 0);
    MyGLRenderer.checkGlError(TAG + " glVertexAttribPointer");


    // Create transform feedback buffer object and bind to transform feedback
    // this creates space in a buffer object for the TransformFeedback.
    int[] tbo = new int[1];
    GLES30.glGenBuffers(1, tbo, 0);
    GLES30.glBindBuffer(GLES30.GL_TRANSFORM_FEEDBACK_BUFFER, tbo[0]);
    GLES30.glBufferData(GLES30.GL_TRANSFORM_FEEDBACK_BUFFER, bufferLength, null, GLES30.GL_STATIC_READ);
    GLES30.glBindBufferBase(GLES30.GL_TRANSFORM_FEEDBACK_BUFFER, 0, tbo[0]); //very important

    MyGLRenderer.checkGlError(TAG + " glBindBufferBase");

    // Disable Rasterizer if you just need the data
    GLES30.glEnable(GLES30.GL_RASTERIZER_DISCARD);

    // Start the TransformFeedback, Draw the Arrays, then End the Transform Feedback
    GLES30.glBeginTransformFeedback(GLES30.GL_POINTS);
    GLES30.glDrawArrays(GLES30.GL_POINTS, 0, 5);
    MyGLRenderer.checkGlError(TAG + " glDrawArrays");
    GLES30.glEndTransformFeedback();

    // Reenable Rasterizer if you need it, which you do if you are drawing anything.
    GLES30.glDisable(GLES30.GL_RASTERIZER_DISCARD);

    // Flush out anything in GL before mapping the buffer.
    GLES30.glFlush();
    MyGLRenderer.checkGlError(TAG + " pre-glMapBufferRange ");

    // Map the transform feedback buffer to local address space.
    Buffer mappedBuffer = GLES30.glMapBufferRange(GLES30.GL_TRANSFORM_FEEDBACK_BUFFER,
    0, bufferLength, GLES30.GL_MAP_READ_BIT);

    // Read out the data, here we write to logcat.
    if (mappedBuffer!=null){
    ByteBuffer transformedBuffer = ((ByteBuffer) mappedBuffer);
    transformedBuffer.order(ByteOrder.LITTLE_ENDIAN);
    MyGLRenderer.checkGlError(TAG + " glMapBufferRange");

    Log.d(TAG, String.format("output values = %f %f %f %f %f\n", transformedBuffer.getFloat(),
    transformedBuffer.getFloat(), transformedBuffer.getFloat(),
    transformedBuffer.getFloat(), transformedBuffer.getFloat()));
    transformedBuffer.position(0);

    }
    // Don't forget to Unmap the Transform Feeback Buffer.
    GLES30.glUnmapBuffer(GLES30.GL_TRANSFORM_FEEDBACK_BUFFER);
    }
    }