测试例子：1122，红色绿色，字号20、 50
cc.dynamicAtlasManager.showDebug(true);
动态图集情况如下：
label.CacheModel="bitmap"，
label.CacheModel="char"
可以观察到无论哪种模式，只要label使用的字号，颜色，字体不同，都会进行单独的渲染，注意这里的颜色，也会受影响，原因是shader里面不处理node color导致的。
即如果label除了颜色剩下的属性都相同，都会生成同等颜色个数的label。
通过spector.js可以找到对应的shader
Creator\2.4.8\resources\static\default-assets\resources\effects\builtin-2d-sprite.effect
// Copyright (c) 2017-2018 Xiamen Yaji Software Co., Ltd.
CCEffect %{
techniques:
- passes:
- vert: vs
frag: fs
blendState:
targets:
- blend: true
rasterizerState:
cullMode: none
properties:
texture: { value: white }
alphaThreshold: { value: 0.5 }
}%
CCProgram vs %{
precision highp float;
#include <cc-global>
#include <cc-local>
in vec3 a_position;
in vec4 a_color;
out vec4 v_color;
#if USE_TEXTURE
in vec2 a_uv0;
out vec2 v_uv0;
#endif
void main () {
vec4 pos = vec4(a_position, 1);
#if CC_USE_MODEL
pos = cc_matViewProj * cc_matWorld * pos;
#else
pos = cc_matViewProj * pos;
#endif
#if USE_TEXTURE
v_uv0 = a_uv0;
#endif
v_color = a_color;
gl_Position = pos;
}
}%
CCProgram fs %{
precision highp float;
#include <alpha-test>
#include <texture>
in vec4 v_color;
#if USE_TEXTURE
in vec2 v_uv0;
uniform sampler2D texture;
#endif
void main () {
vec4 o = vec4(1, 1, 1, 1);
#if USE_TEXTURE
CCTexture(texture, v_uv0, o);
#endif
o *= v_color;
ALPHA_TEST(o);
#if USE_BGRA
gl_FragColor = o.bgra;
#else
gl_FragColor = o.rgba;
#endif
}
}%
展开后的shader：
#define USE_TEXTURE 1
#define CC_USE_MODEL 0
#define USE_ALPHA_TEST 0
#define CC_USE_ALPHA_ATLAS_texture 0
#define INPUT_IS_GAMMA 0
#define USE_BGRA 0
precision highp float;
uniform mat4 cc_matViewProj;
uniform mat4 cc_matWorld;
attribute vec3 a_position;
attribute vec4 a_color;
varying vec4 v_color;
#if USE_TEXTURE
attribute vec2 a_uv0;
varying vec2 v_uv0;
#endif
void main () {
vec4 pos = vec4(a_position, 1);
#if CC_USE_MODEL
pos = cc_matViewProj * cc_matWorld * pos;
#else
pos = cc_matViewProj * pos;
#endif
#if USE_TEXTURE
v_uv0 = a_uv0;
#endif
v_color = a_color;
gl_Position = pos;
}
#define USE_TEXTURE 1
#define CC_USE_MODEL 0
#define USE_ALPHA_TEST 0
#define CC_USE_ALPHA_ATLAS_texture 0
#define INPUT_IS_GAMMA 0
#define USE_BGRA 0
precision highp float;
#if USE_ALPHA_TEST
uniform float alphaThreshold;
#endif
void ALPHA_TEST (in vec4 color) {
#if USE_ALPHA_TEST
if (color.a < alphaThreshold) discard;
#endif
}
void ALPHA_TEST (in float alpha) {
#if USE_ALPHA_TEST
if (alpha < alphaThreshold) discard;
#endif
}
varying vec4 v_color;
#if USE_TEXTURE
varying vec2 v_uv0;
uniform sampler2D texture;
#endif
void main () {
vec4 o = vec4(1, 1, 1, 1);
#if USE_TEXTURE
vec4 texture_tmp = texture2D(texture, v_uv0);
#if CC_USE_ALPHA_ATLAS_texture
texture_tmp.a *= texture2D(texture, v_uv0 + vec2(0, 0.5)).r;
#endif
#if INPUT_IS_GAMMA
o.rgb *= (texture_tmp.rgb * texture_tmp.rgb);
o.a *= texture_tmp.a;
#else
o *= texture_tmp;
#endif
#endif
o *= v_color;
ALPHA_TEST(o);
#if USE_BGRA
gl_FragColor = o.bgra;
#else
gl_FragColor = o.rgba;
#endif
}
可以看到
o*=v_color;
如果字符纹理都是白色的，顶点颜色v_color如果传递过来相乘，是能够得到正确的颜色的
那为啥creator不这么做呢？
Creator\2.4.8\resources\engine\cocos2d\core\renderer\webgl\assemblers\label\2d\letter.js
_getColor (comp) {
WHITE._fastSetA(comp.node._color.a);
return WHITE._val;
}
updateColor (comp) {
let color = this._getColor(comp);
super.updateColor(comp, color);
}
可以看到在组装数据的时候，会舍弃掉node.color的颜色，只保留透明度，看来还是有优化空间的
混合有bug导致这么做
