我正在尝试屏蔽一个精灵,所以我写了一个简单的片段着色器,它只渲染未隐藏在另一个纹理(掩码)下的像素。问题是,在通过着色器后,我的纹理似乎有y坐标偏移。
这是我要屏蔽的精灵(GroundZone)的init方法:
bool GroundZone::initWithSize(Size size) {
// [...]
// Setup the mask of the sprite
m_mask = RenderTexture::create(textureWidth, textureHeight);
m_mask->retain();
m_mask->setKeepMatrix(true);
Texture2D *maskTexture = m_mask->getSprite()->getTexture();
maskTexture->setAliasTexParameters(); // Disable linear interpolation on the mask
// Load the custom frag shader with a default vert shader as the sprite’s program
FileUtils *fileUtils = FileUtils::getInstance();
string vertexSource = ccPositionTextureA8Color_vert;
string fragmentSource = fileUtils->getStringFromFile(
fileUtils->fullPathForFilename("CustomShader_AlphaMask_frag.fsh"));
GLProgram *shader = new GLProgram;
shader->initWithByteArrays(vertexSource.c_str(), fragmentSource.c_str());
shader->bindAttribLocation(GLProgram::ATTRIBUTE_NAME_POSITION, GLProgram::VERTEX_ATTRIB_POSITION);
shader->bindAttribLocation(GLProgram::ATTRIBUTE_NAME_TEX_COORD, GLProgram::VERTEX_ATTRIB_TEX_COORDS);
shader->link();
CHECK_GL_ERROR_DEBUG();
shader->updateUniforms();
CHECK_GL_ERROR_DEBUG();
int maskTexUniformLoc = shader->getUniformLocationForName("u_alphaMaskTexture");
shader->setUniformLocationWith1i(maskTexUniformLoc, 1);
this->setShaderProgram(shader);
shader->release();
// [...]
}
这些是用于在精灵上实际绘制蒙版的自定义绘图方法:
您需要知道m_mask
是由另一个类在外部修改的,onDraw()
方法只会渲染它。
void GroundZone::draw(Renderer *renderer, const kmMat4 &transform, bool transformUpdated) {
m_renderCommand.init(_globalZOrder);
m_renderCommand.func = CC_CALLBACK_0(GroundZone::onDraw, this, transform, transformUpdated);
renderer->addCommand(&m_renderCommand);
Sprite::draw(renderer, transform, transformUpdated);
}
void GroundZone::onDraw(const kmMat4 &transform, bool transformUpdated) {
GLProgram *shader = this->getShaderProgram();
shader->use();
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, m_mask->getSprite()->getTexture()->getName());
glActiveTexture(GL_TEXTURE0);
}
下面是方法(位于另一个类,GroundLayer中),它通过从点start
到点end
绘制一条线来修改蒙版。两个点都在Cocos2d坐标中(点(0,0)是左下角)。
void GroundLayer::drawTunnel(Point start, Point end) {
// To dig a line, we need first to get the texture of the zone we will be digging into. Then we get the
// relative position of the start and end point in the zone's node space. Finally we use the custom shader to
// draw a mask over the existing texture.
for (auto it = _children.begin(); it != _children.end(); it++) {
GroundZone *zone = static_cast<GroundZone *>(*it);
Point nodeStart = zone->convertToNodeSpace(start);
Point nodeEnd = zone->convertToNodeSpace(end);
// Now that we have our two points converted to node space, it's easy to draw a mask that contains a line
// going from the start point to the end point and that is then applied over the current texture.
Size groundZoneSize = zone->getContentSize();
RenderTexture *rt = zone->getMask();
rt->begin(); {
// Draw a line going from start and going to end in the texture, the line will act as a mask over the
// existing texture
DrawNode *line = DrawNode::create();
line->retain();
line->drawSegment(nodeStart, nodeEnd, 20, Color4F::RED);
line->visit();
} rt->end();
}
}
最后,这是我写的自定义着色器。
#ifdef GL_ES
precision mediump float;
#endif
varying vec2 v_texCoord;
uniform sampler2D u_texture;
uniform sampler2D u_alphaMaskTexture;
void main() {
float maskAlpha = texture2D(u_alphaMaskTexture, v_texCoord).a;
float texAlpha = texture2D(u_texture, v_texCoord).a;
float blendAlpha = (1.0 - maskAlpha) * texAlpha; // Show only where mask is invisible
vec3 texColor = texture2D(u_texture, v_texCoord).rgb;
gl_FragColor = vec4(texColor, blendAlpha);
return;
}
我遇到了y坐标的问题。事实上,似乎一旦它通过我的自定义着色器,精灵的纹理就不在正确的位置:
没有自定义着色器(精灵是棕色的东西):
使用自定义着色器:
这里发生了什么?谢谢:))
答案 0 :(得分:5)
找到解决方案。 vert着色器不应该使用MVP矩阵,所以我加载了ccPositionTextureColor_noMVP_vert
而不是ccPositionTextureA8Color_vert
。
答案 1 :(得分:0)
在你的vert着色器(.vsh)中,你的main方法应该是这样的:
attribute vec4 a_position;
attribute vec2 a_texCoord;
attribute vec4 a_color;
varying vec4 v_fragmentColor;
varying vec2 v_texCoord;
void main()
{
//CC_PMatrix is the projection matrix, where as the CC_MVPMatrix is the model, view, projection matrix. Since in 2d we are using ortho camera CC_PMatrix is enough to do calculations.
//gl_Position = CC_MVPMatrix * a_position;
gl_Position = CC_PMatrix * a_position;
v_fragmentColor = a_color;
v_texCoord = a_texCoord;
}
请注意,我们使用CC_PMatrix
代替CC_MVPMatrix
。