void ClippingNode::onBeforeVisit() { /////////////////////////////////// // INIT // increment the current layer s_layer++; // mask of the current layer (ie: for layer 3: 00000100) GLint mask_layer = 0x1 << s_layer; // mask of all layers less than the current (ie: for layer 3: 00000011) GLint mask_layer_l = mask_layer - 1; // mask of all layers less than or equal to the current (ie: for layer 3: 00000111) _mask_layer_le = mask_layer | mask_layer_l; // manually save the stencil state _currentStencilEnabled = glIsEnabled(GL_STENCIL_TEST); glGetIntegerv(GL_STENCIL_WRITEMASK, (GLint *)&_currentStencilWriteMask); glGetIntegerv(GL_STENCIL_FUNC, (GLint *)&_currentStencilFunc); glGetIntegerv(GL_STENCIL_REF, &_currentStencilRef); glGetIntegerv(GL_STENCIL_VALUE_MASK, (GLint *)&_currentStencilValueMask); glGetIntegerv(GL_STENCIL_FAIL, (GLint *)&_currentStencilFail); glGetIntegerv(GL_STENCIL_PASS_DEPTH_FAIL, (GLint *)&_currentStencilPassDepthFail); glGetIntegerv(GL_STENCIL_PASS_DEPTH_PASS, (GLint *)&_currentStencilPassDepthPass); // enable stencil use glEnable(GL_STENCIL_TEST); // check for OpenGL error while enabling stencil test CHECK_GL_ERROR_DEBUG(); // all bits on the stencil buffer are readonly, except the current layer bit, // this means that operation like glClear or glStencilOp will be masked with this value glStencilMask(mask_layer); // manually save the depth test state glGetBooleanv(GL_DEPTH_WRITEMASK, &_currentDepthWriteMask); // disable depth test while drawing the stencil //glDisable(GL_DEPTH_TEST); // disable update to the depth buffer while drawing the stencil, // as the stencil is not meant to be rendered in the real scene, // it should never prevent something else to be drawn, // only disabling depth buffer update should do glDepthMask(GL_FALSE); /////////////////////////////////// // CLEAR STENCIL BUFFER // manually clear the stencil buffer by drawing a fullscreen rectangle on it // setup the stencil test func like this: // for each pixel in the fullscreen rectangle // never draw it into the frame buffer // if not in inverted mode: set the current layer value to 0 in the stencil buffer // if in inverted mode: set the current layer value to 1 in the stencil buffer glStencilFunc(GL_NEVER, mask_layer, mask_layer); glStencilOp(!_inverted ? GL_ZERO : GL_REPLACE, GL_KEEP, GL_KEEP); // draw a fullscreen solid rectangle to clear the stencil buffer //ccDrawSolidRect(Point::ZERO, ccpFromSize([[Director sharedDirector] winSize]), Color4F(1, 1, 1, 1)); drawFullScreenQuadClearStencil(); /////////////////////////////////// // DRAW CLIPPING STENCIL // setup the stencil test func like this: // for each pixel in the stencil node // never draw it into the frame buffer // if not in inverted mode: set the current layer value to 1 in the stencil buffer // if in inverted mode: set the current layer value to 0 in the stencil buffer glStencilFunc(GL_NEVER, mask_layer, mask_layer); glStencilOp(!_inverted ? GL_REPLACE : GL_ZERO, GL_KEEP, GL_KEEP); // enable alpha test only if the alpha threshold < 1, // indeed if alpha threshold == 1, every pixel will be drawn anyways if (_alphaThreshold < 1) { #if (CC_TARGET_PLATFORM == CC_PLATFORM_MAC || CC_TARGET_PLATFORM == CC_PLATFORM_WINDOWS || CC_TARGET_PLATFORM == CC_PLATFORM_LINUX) // manually save the alpha test state _currentAlphaTestEnabled = glIsEnabled(GL_ALPHA_TEST); glGetIntegerv(GL_ALPHA_TEST_FUNC, (GLint *)&_currentAlphaTestFunc); glGetFloatv(GL_ALPHA_TEST_REF, &_currentAlphaTestRef); // enable alpha testing glEnable(GL_ALPHA_TEST); // check for OpenGL error while enabling alpha test CHECK_GL_ERROR_DEBUG(); // pixel will be drawn only if greater than an alpha threshold glAlphaFunc(GL_GREATER, _alphaThreshold); #else #endif } //Draw _stencil }
void BeginStencilCommand::execute() { // increment the current layer ++_layer; ++_stencilCount; auto state = getCurrentState(); // enable stencil use if (1 == _stencilCount) glEnable(GL_STENCIL_TEST); // check for OpenGL error while enabling stencil test CHECK_GL_ERROR_DEBUG(); // all bits on the stencil buffer are readonly, except the current layer bit, // this means that operation like glClear or glStencilOp will be masked with this value glStencilMask(state._mask_layer); // manually save the depth test state glGetBooleanv(GL_DEPTH_WRITEMASK, &state._depthWriteMask); _stencilStates.push(state); if (_clearStencil) { // disable depth test while drawing the stencil //glDisable(GL_DEPTH_TEST); // disable update to the depth buffer while drawing the stencil, // as the stencil is not meant to be rendered in the real scene, // it should never prevent something else to be drawn, // only disabling depth buffer update should do glDepthMask(GL_FALSE); // manually clear the stencil buffer by drawing a fullscreen rectangle on it // setup the stencil test func like this: // for each pixel in the fullscreen rectangle // never draw it into the frame buffer // if not in inverted mode: set the current layer value to 0 in the stencil buffer // if in inverted mode: set the current layer value to 1 in the stencil buffer glStencilFunc(GL_NEVER, state._mask_layer, state._mask_layer); glStencilOp(!_inverted ? GL_ZERO : GL_REPLACE, GL_KEEP, GL_KEEP); // draw a fullscreen solid rectangle to clear the stencil buffer drawFullScreenQuadClearStencil(); } // setup the stencil test func like this: // for each pixel in the stencil node // never draw it into the frame buffer // if not in inverted mode: set the current layer value to 1 in the stencil buffer // if in inverted mode: set the current layer value to 0 in the stencil buffer glStencilFunc(GL_NEVER, state._mask_layer, state._mask_layer); glStencilOp(!_inverted ? GL_REPLACE : GL_ZERO, GL_KEEP, GL_KEEP); // enable alpha test only if the alpha threshold < 1, // indeed if alpha threshold == 1, every pixel will be drawn anyways if (_alphaThreshold < 1) { #if (CC_TARGET_PLATFORM == CC_PLATFORM_MAC || CC_TARGET_PLATFORM == CC_PLATFORM_WIN32 || CC_TARGET_PLATFORM == CC_PLATFORM_LINUX) // manually save the alpha test state // _currentAlphaTestEnabled = glIsEnabled(GL_ALPHA_TEST); // glGetIntegerv(GL_ALPHA_TEST_FUNC, (GLint *)&_currentAlphaTestFunc); // glGetFloatv(GL_ALPHA_TEST_REF, &_currentAlphaTestRef); // enable alpha testing glEnable(GL_ALPHA_TEST); // check for OpenGL error while enabling alpha test CHECK_GL_ERROR_DEBUG(); // pixel will be drawn only if greater than an alpha threshold glAlphaFunc(GL_GREATER, _alphaThreshold); #else #endif } }