Sprite: Add special case shader for translucent effect

Translucent sprites (opacity < 255) are very common,
so using a custom shader instead of the full blown effect one
helps a lot, especially on mobile.

CMakeLists.txt

@@ -220,6 +220,7 @@ set(EMBEDDED_INPUT
 	shader/simple.frag
 	shader/simpleColor.frag
 	shader/simpleAlpha.frag
+	shader/simpleAlphaUni.frag
 	shader/flashMap.frag
 	shader/simple.vert
 	shader/simpleColor.vert

mkxp.pro

@@ -193,6 +193,7 @@ EMBED = \
 	shader/simple.frag \
 	shader/simpleColor.frag \
 	shader/simpleAlpha.frag \
+	shader/simpleAlphaUni.frag \
 	shader/flashMap.frag \
 	shader/simple.vert \
 	shader/simpleColor.vert \

shader/simpleAlphaUni.frag

@@ -0,0 +1,11 @@
+
+uniform sampler2D texture;
+uniform lowp float alpha;
+
+varying vec2 v_texCoord;
+
+void main()
+{
+	gl_FragColor = texture2D(texture, v_texCoord);
+	gl_FragColor.a *= alpha;
+}

src/shader.cpp

@@ -38,6 +38,7 @@
 #include "simple.frag.xxd"
 #include "simpleColor.frag.xxd"
 #include "simpleAlpha.frag.xxd"
+#include "simpleAlphaUni.frag.xxd"
 #include "flashMap.frag.xxd"
 #include "simple.vert.xxd"
 #include "simpleColor.vert.xxd"
@@ -314,6 +315,27 @@ void SimpleSpriteShader::setSpriteMat(const float value[16])
 }
 
 
+AlphaSpriteShader::AlphaSpriteShader()
+{
+	INIT_SHADER(sprite, simpleAlphaUni, AlphaSpriteShader);
+
+	ShaderBase::init();
+
+	GET_U(spriteMat);
+	GET_U(alpha);
+}
+
+void AlphaSpriteShader::setSpriteMat(const float value[16])
+{
+	gl.UniformMatrix4fv(u_spriteMat, 1, GL_FALSE, value);
+}
+
+void AlphaSpriteShader::setAlpha(float value)
+{
+	gl.Uniform1f(u_alpha, value);
+}
+
+
 TransShader::TransShader()
 {
 	INIT_SHADER(simple, trans, TransShader);

src/shader.h

@@ -121,6 +121,18 @@ private:
 	GLint u_spriteMat;
 };
 
+class AlphaSpriteShader : public ShaderBase
+{
+public:
+	AlphaSpriteShader();
+
+	void setSpriteMat(const float value[16]);
+	void setAlpha(float value);
+
+private:
+	GLint u_spriteMat, u_alpha;
+};
+
 class TransShader : public ShaderBase
 {
 public:
@@ -277,6 +289,7 @@ struct ShaderSet
 	SimpleColorShader simpleColor;
 	SimpleAlphaShader simpleAlpha;
 	SimpleSpriteShader simpleSprite;
+	AlphaSpriteShader alphaSprite;
 	SpriteShader sprite;
 	PlaneShader plane;
 	TilemapShader tilemap;

src/sprite.cpp

@@ -515,7 +515,6 @@ void Sprite::draw()
 
 	bool renderEffect = p->color->hasEffect() ||
 	                    p->tone->hasEffect()  ||
-	                    p->opacity != 255     ||
 	                    flashing              ||
 	                    p->bushDepth != 0;
 
@@ -541,6 +540,16 @@ void Sprite::draw()
 
 		base = &shader;
 	}
+	else if (p->opacity != 255)
+	{
+		AlphaSpriteShader &shader = shState->shaders().alphaSprite;
+		shader.bind();
+
+		shader.setSpriteMat(p->trans.getMatrix());
+		shader.setAlpha(p->opacity.norm);
+		shader.applyViewportProj();
+		base = &shader;
+	}
 	else
 	{
 		SimpleSpriteShader &shader = shState->shaders().simpleSprite;