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Diffstat (limited to 'docs/html/training/graphics/opengl/projection.jd')
| -rw-r--r-- | docs/html/training/graphics/opengl/projection.jd | 48 |
1 files changed, 40 insertions, 8 deletions
diff --git a/docs/html/training/graphics/opengl/projection.jd b/docs/html/training/graphics/opengl/projection.jd index b09e74c..356d5d4 100644 --- a/docs/html/training/graphics/opengl/projection.jd +++ b/docs/html/training/graphics/opengl/projection.jd @@ -71,6 +71,11 @@ projection transformation {@link android.opengl.Matrix} using the {@link android.opengl.Matrix#frustumM Matrix.frustumM()} method:</p> <pre> +// mMVPMatrix is an abbreviation for "Model View Projection Matrix" +private final float[] mMVPMatrix = new float[16]; +private final float[] mProjectionMatrix = new float[16]; +private final float[] mViewMatrix = new float[16]; + @Override public void onSurfaceChanged(GL10 unused, int width, int height) { GLES20.glViewport(0, 0, width, height); @@ -95,10 +100,10 @@ view transformation in order for anything to show up on screen.</p> <h2 id="camera-view">Define a Camera View</h2> <p>Complete the process of transforming your drawn objects by adding a camera view transformation as -part of the drawing process. In the following example code, the camera view transformation is -calculated using the {@link android.opengl.Matrix#setLookAtM Matrix.setLookAtM()} method and then -combined with the previously calculated projection matrix. The combined transformation matrices -are then passed to the drawn shape.</p> +part of the drawing process in your renderer. In the following example code, the camera view +transformation is calculated using the {@link android.opengl.Matrix#setLookAtM Matrix.setLookAtM()} +method and then combined with the previously calculated projection matrix. The combined +transformation matrices are then passed to the drawn shape.</p> <pre> @Override @@ -119,7 +124,32 @@ public void onDrawFrame(GL10 unused) { <h2 id="#transform">Apply Projection and Camera Transformations</h2> <p>In order to use the combined projection and camera view transformation matrix shown in the -previews sections, modify the {@code draw()} method of your graphic objects to accept the combined +previews sections, first add a matrix variable to the <em>vertex shader</em> previously defined +in the <code>Triangle</code> class:</p> + +<pre> +public class Triangle { + + private final String vertexShaderCode = + // This matrix member variable provides a hook to manipulate + // the coordinates of the objects that use this vertex shader + <strong>"uniform mat4 uMVPMatrix;" +</strong> + "attribute vec4 vPosition;" + + "void main() {" + + // the matrix must be included as a modifier of gl_Position + // Note that the uMVPMatrix factor *must be first* in order + // for the matrix multiplication product to be correct. + " gl_Position = <strong>uMVPMatrix</strong> * vPosition;" + + "}"; + + // Use to access and set the view transformation + private int mMVPMatrixHandle; + + ... +} +</pre> + +<p>Next, modify the {@code draw()} method of your graphic objects to accept the combined transformation matrix and apply it to the shape:</p> <pre> @@ -127,14 +157,16 @@ public void draw(float[] mvpMatrix) { // pass in the calculated transformation m ... // get handle to shape's transformation matrix - mMVPMatrixHandle = GLES20.glGetUniformLocation(mProgram, "uMVPMatrix"); + <strong>mMVPMatrixHandle = GLES20.glGetUniformLocation(mProgram, "uMVPMatrix");</strong> // Pass the projection and view transformation to the shader - GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mvpMatrix, 0); + <strong>GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mvpMatrix, 0);</strong> // Draw the triangle GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, vertexCount); - ... + + // Disable vertex array + GLES20.glDisableVertexAttribArray(mPositionHandle); } </pre> |