diff options
Diffstat (limited to 'src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp')
| -rw-r--r-- | src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp | 58 |
1 files changed, 29 insertions, 29 deletions
diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp index 8ca2fd4..f52ed92 100644 --- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp +++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp @@ -583,37 +583,37 @@ void QGL2PaintEngineExPrivate::updateMatrix() { // qDebug("QGL2PaintEngineExPrivate::updateMatrix()"); - // We set up the 4x4 transformation matrix on the vertex shaders to - // be the equivalent of glOrtho(0, w, h, 0, -1, 1) * transform: - // - // | 2/width 0 0 -1 | | m11 m21 0 dx | - // | 0 -2/height 0 1 | | m12 m22 0 dy | - // | 0 0 -1 0 | * | 0 0 1 0 | - // | 0 0 0 1 | | m13 m23 0 m33 | - // - // We expand out the multiplication to save the cost of a full 4x4 - // matrix multiplication as most of the components are trivial. const QTransform& transform = q->state()->matrix; - qreal wfactor = 2.0 / width; - qreal hfactor = -2.0 / height; - - pmvMatrix[0][0] = wfactor * transform.m11() - transform.m13(); - pmvMatrix[0][1] = hfactor * transform.m12() + transform.m13(); - pmvMatrix[0][2] = 0.0; - pmvMatrix[0][3] = transform.m13(); - pmvMatrix[1][0] = wfactor * transform.m21() - transform.m23(); - pmvMatrix[1][1] = hfactor * transform.m22() + transform.m23(); - pmvMatrix[1][2] = 0.0; - pmvMatrix[1][3] = transform.m23(); - pmvMatrix[2][0] = 0.0; - pmvMatrix[2][1] = 0.0; - pmvMatrix[2][2] = -1.0; - pmvMatrix[2][3] = 0.0; - pmvMatrix[3][0] = wfactor * transform.dx() - transform.m33(); - pmvMatrix[3][1] = hfactor * transform.dy() + transform.m33(); - pmvMatrix[3][2] = 0.0; - pmvMatrix[3][3] = transform.m33(); + // The projection matrix converts from Qt's coordinate system to GL's coordinate system + // * GL's viewport is 2x2, Qt's is width x height + // * GL has +y -> -y going from bottom -> top, Qt is the other way round + // * GL has [0,0] in the center, Qt has it in the top-left + // + // This results in the Projection matrix below, which is multiplied by the painter's + // transformation matrix, as shown below: + // + // Projection Matrix Painter Transform + // ------------------------------------------------ ------------------------ + // | 2.0 / width | 0.0 | -1.0 | | m11 | m21 | dx | + // | 0.0 | -2.0 / height | 1.0 | * | m12 | m22 | dy | + // | 0.0 | 0.0 | 1.0 | | m13 | m23 | m33 | + // ------------------------------------------------ ------------------------ + // + // NOTE: The resultant matrix is also transposed, as GL expects column-major matracies + + const GLfloat wfactor = 2.0f / width; + const GLfloat hfactor = -2.0f / height; + + pmvMatrix[0][0] = (wfactor * transform.m11()) - transform.m13(); + pmvMatrix[1][0] = (wfactor * transform.m21()) - transform.m23(); + pmvMatrix[2][0] = (wfactor * transform.dx() ) - transform.m33(); + pmvMatrix[0][1] = (hfactor * transform.m12()) + transform.m13(); + pmvMatrix[1][1] = (hfactor * transform.m22()) + transform.m23(); + pmvMatrix[2][1] = (hfactor * transform.dy() ) + transform.m33(); + pmvMatrix[0][2] = transform.m13(); + pmvMatrix[1][2] = transform.m23(); + pmvMatrix[2][2] = transform.m33(); // 1/10000 == 0.0001, so we have good enough res to cover curves // that span the entire widget... |