Databases
StackOverflow2013
Postsdbo
PORotating a shape about its axis then translating the shape in OpenGL ES 2.0
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PORotating a shape about its axis then translating the shape in OpenGL ES 2.0
    primarykey
    data
    text
    <p>I'm trying to rotate a triangle about its centre (0, 0, 0) and then translate it by (0.5, 0.5, 0). However, no matter if I place the <em>translateM</em> command before or after the <em>rotateM</em> commands I still get the same result, which is a triangle translated to the said position, rotating (orbiting if you like) about (0, 0, 0). I've looked online and found similar posts, but they don't help. Here is my code:</p> <p>Note: my triangles are all centred on (0, 0, 0) to begin with.</p> <pre><code> Matrix.setIdentityM(mModelMatrix, 0); // *** transform shape before rendering Matrix.setRotateM(mRotationMatrix, 0, rx, -1.0f, 0, 0); Matrix.multiplyMM(mModelMatrix, 0, mRotationMatrix, 0, mModelMatrix, 0); // rotate Matrix.setRotateM(mRotationMatrix, 0, ry, 0, -1.0f, 0); Matrix.multiplyMM(mModelMatrix, 0, mRotationMatrix, 0, mModelMatrix, 0); // rotate Matrix.setRotateM(mRotationMatrix, 0, rz, 0, 0, -1.0f); Matrix.multiplyMM(mModelMatrix, 0, mRotationMatrix, 0, mModelMatrix, 0); // rotate Matrix.translateM(mModelMatrix, 0, tx, ty, tz); // translate Matrix.multiplyMM(mvpMatrix, 0, mModelMatrix, 0, mvpMatrix, 0); // world view // *** render // Add program to OpenGL environment GLES20.glUseProgram(mProgram); // get handle to vertex shader's vPosition member mPositionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition"); // Enable a handle to the triangle vertices GLES20.glEnableVertexAttribArray(mPositionHandle); // Prepare the triangle coordinate data GLES20.glVertexAttribPointer(mPositionHandle, COORDS_PER_VERTEX, GLES20.GL_FLOAT, false, vertexStride, vertexBuffer); // get handle to fragment shader's vColor member mColorHandle = GLES20.glGetUniformLocation(mProgram, "vColor"); // Set color for drawing the triangle GLES20.glUniform4fv(mColorHandle, 1, color, 0); // get handle to shape's transformation matrix mMVPMatrixHandle = GLES20.glGetUniformLocation(mProgram, "uMVPMatrix"); MyGL20Renderer.checkGlError("glGetUniformLocation"); // Apply the projection and view transformation GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mvpMatrix, 0); MyGL20Renderer.checkGlError("glUniformMatrix4fv"); // Draw the triangle GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, vertexCount); // Disable vertex array GLES20.glDisableVertexAttribArray(mPositionHandle); </code></pre> <p>Any suggestions would be appreciated.</p>
    singulars
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PTQuestion
    1. USAntinous
    1. USAntinous
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. COProbably there is something wrong with your matrix multiplication logic. As far as I know, the operation that you want first is multiplied last, so your multiplication order should be first translation and then rotation. Finally, it would be better if we could see your matrix multiplication code either.
      singulars
      1. PORotating a shape about its axis then translating the shape in OpenGL ES 2.0
      1. USeozgonul
    2. COThat's what the problem was. I needed to translate first, then rotate, and the order of matrix operands was wrong.
      singulars
      1. PORotating a shape about its axis then translating the shape in OpenGL ES 2.0
      1. USAntinous
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload