java - 在一个 3D 对象上应用旋转后更新 View OpenGL ES 2.0

Question

我一直在为 Android Studio 开发一个基于 ARCore 示例的应用程序。我已经成功地将我选择的不同对象带入 View 中，现在我尝试仅旋转一个对象，即最后放置的对象。这意味着当选择一个对象时，我应该能够旋转它并改变它的位置，直到我选择另一个对象。我不应该再能够操纵那个物体了。现在这是我的 draw() 方法，为每个放置的对象调用该方法

public void draw(float[] cameraView, float[] cameraPerspective, float lightIntensity) {

    ShaderUtil.checkGLError(TAG, "Before draw");

    // Build the ModelView and ModelViewProjection matrices
    // for calculating object position and light.
    Matrix.multiplyMM(modelViewMatrix, 0, cameraView, 0, modelMatrix, 0);
    Matrix.multiplyMM(modelViewProjectionMatrix, 0, cameraPerspective, 0, modelViewMatrix, 0);



    if(this.movable==true) {
      //rotation
      Matrix.setRotateM(mRotationMatrix, 0, FactorsClass.rotateF, 0.0f, 1.0f, 0.0f);
      Matrix.multiplyMM(mFinalModelViewProjectionMatrix, 0, modelViewProjectionMatrix, 0, mRotationMatrix, 0);
    }

    GLES20.glUseProgram(program);

    // Set the lighting environment properties.
    Matrix.multiplyMV(viewLightDirection, 0, modelViewMatrix, 0, LIGHT_DIRECTION, 0);
    normalizeVec3(viewLightDirection);
    GLES20.glUniform4f(
        lightingParametersUniform,
        viewLightDirection[0],
        viewLightDirection[1],
        viewLightDirection[2],
        lightIntensity);

    // Set the object material properties.
    GLES20.glUniform4f(materialParametersUniform, ambient, diffuse, specular, specularPower);

    // Attach the object texture.
    GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
    GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textures[0]);
    GLES20.glUniform1i(textureUniform, 0);

    // Set the vertex attributes.
    GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, vertexBufferId);

    GLES20.glVertexAttribPointer(
        positionAttribute, COORDS_PER_VERTEX, GLES20.GL_FLOAT, false, 0, verticesBaseAddress);
    GLES20.glVertexAttribPointer(normalAttribute, 3, GLES20.GL_FLOAT, false, 0, normalsBaseAddress);
    GLES20.glVertexAttribPointer(
        texCoordAttribute, 2, GLES20.GL_FLOAT, false, 0, texCoordsBaseAddress);

    GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, 0);

    // Set the ModelViewProjection matrix in the shader.
    GLES20.glUniformMatrix4fv(modelViewUniform, 1, false, modelViewMatrix, 0);


      GLES20.glUniformMatrix4fv(modelViewProjectionUniform, 1, false, modelViewProjectionMatrix, 0);
      if(this.movable==true) {
        GLES20.glUniformMatrix4fv(modelViewProjectionUniform, 1, false, mFinalModelViewProjectionMatrix, 0);
      }


    // Enable vertex arrays
    GLES20.glEnableVertexAttribArray(positionAttribute);
    GLES20.glEnableVertexAttribArray(normalAttribute);
    GLES20.glEnableVertexAttribArray(texCoordAttribute);

    if (blendMode != null) {
      GLES20.glDepthMask(false);
      GLES20.glEnable(GLES20.GL_BLEND);
      switch (blendMode) {
        case Shadow:
          // Multiplicative blending function for Shadow.
          GLES20.glBlendFunc(GLES20.GL_ZERO, GLES20.GL_ONE_MINUS_SRC_ALPHA);
          break;
        case Grid:
          // Grid, additive blending function.
          GLES20.glBlendFunc(GLES20.GL_SRC_ALPHA, GLES20.GL_ONE_MINUS_SRC_ALPHA);
          break;
      }
    }

    GLES20.glBindBuffer(GLES20.GL_ELEMENT_ARRAY_BUFFER, indexBufferId);
    GLES20.glDrawElements(GLES20.GL_TRIANGLES, indexCount, GLES20.GL_UNSIGNED_SHORT, 0);
    GLES20.glBindBuffer(GLES20.GL_ELEMENT_ARRAY_BUFFER, 0);

    if (blendMode != null) {
      GLES20.glDisable(GLES20.GL_BLEND);
      GLES20.glDepthMask(true);
    }

    // Disable vertex arrays
    GLES20.glDisableVertexAttribArray(positionAttribute);
    GLES20.glDisableVertexAttribArray(normalAttribute);
    GLES20.glDisableVertexAttribArray(texCoordAttribute);

    GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, 0);

    ShaderUtil.checkGLError(TAG, "After draw");
  }

目前，我可以按照自己的意愿旋转一个对象(当可移动变量为 true 时，这意味着它是场景中放置的最后一个对象)，但是一旦我选择另一个对象，旧对象就会返回到其初始位置，就好像它从未旋转过一样。如何更新矩阵以便保持旋转？谢谢!

Answer 1

but once I select another one, the old object returns to its initial position, as if it was never rotated. How can I update the matrix so that the rotations remain applied?

我假设mRotationMatrix是该类的成员。确保 mRotationMatrix 由单位矩阵 intilaized。

如果this.movable==true，则更新mRotationMatrix，但在任何情况下都使用mRotationMatrix来计算mFinalModelViewProjectionMatrix。在任何情况下都使用 mFinalModelViewProjectionMatrix 来设置 modelViewProjectionUniform。

public void draw(float[] cameraView, float[] cameraPerspective, float lightIntensity) {

    .....

    Matrix.multiplyMM(modelViewMatrix, 0, cameraView, 0, modelMatrix, 0);
    Matrix.multiplyMM(modelViewProjectionMatrix, 0, cameraPerspective, 0, modelViewMatrix, 0);


    if(this.movable==true) {
        Matrix.setRotateM(mRotationMatrix, 0, FactorsClass.rotateF, 0.0f, 1.0f, 0.0f);
    }
    Matrix.multiplyMM(mFinalModelViewProjectionMatrix, 0, modelViewProjectionMatrix, 0, mRotationMatrix, 0);

    .....

    GLES20.glUniformMatrix4fv(modelViewProjectionUniform, 1, false, mFinalModelViewProjectionMatrix, 0);

    .....
}