Improve bloom effect (#12916)

* Remove the built-in exposure factor of 2.5
* Add physics-based bloom (https://learnopengl.com/Guest-Articles/2022/Phys.-Based-Bloom)
* Add luminance scaling for bloom layer to simulate HDR
* Add setting to control bloom strength

client/shaders/bloom_downsample/opengl_fragment.glsl

@@ -0,0 +1,37 @@
+// based on Phys.Bloom OpenGL tutorial https://learnopengl.com/Guest-Articles/2022/Phys.-Based-Bloom
+// and ACM Siggraph talk in 2014 by Jorge Jimenez for Call of Duty: Advanced Warfare.
+#define rendered texture0
+
+uniform sampler2D rendered;
+uniform vec2 texelSize0;
+
+#ifdef GL_ES
+varying mediump vec2 varTexCoord;
+#else
+centroid varying vec2 varTexCoord;
+#endif
+
+void main(void)
+{
+	vec2 tx = 2.0 * texelSize0;
+	vec3 a = texture2D(rendered, varTexCoord.st + vec2(-1., -1.) * tx).rgb;
+	vec3 b = texture2D(rendered, varTexCoord.st + vec2(0., -1.) * tx).rgb;
+	vec3 c = texture2D(rendered, varTexCoord.st + vec2(1., -1.) * tx).rgb;
+	vec3 d = texture2D(rendered, varTexCoord.st + vec2(-1., 0.) * tx).rgb;
+	vec3 e = texture2D(rendered, varTexCoord.st + vec2(0., 0.) * tx).rgb;
+	vec3 f = texture2D(rendered, varTexCoord.st + vec2(1., 0.) * tx).rgb;
+	vec3 g = texture2D(rendered, varTexCoord.st + vec2(-1., 1.) * tx).rgb;
+	vec3 h = texture2D(rendered, varTexCoord.st + vec2(0., 1.) * tx).rgb;
+	vec3 i = texture2D(rendered, varTexCoord.st + vec2(1., 1.) * tx).rgb;
+	vec3 j = texture2D(rendered, varTexCoord.st + vec2(-0.5, -0.5) * tx).rgb;
+	vec3 k = texture2D(rendered, varTexCoord.st + vec2(0.5, -0.5) * tx).rgb;
+	vec3 l = texture2D(rendered, varTexCoord.st + vec2(-0.5, 0.5) * tx).rgb;
+	vec3 m = texture2D(rendered, varTexCoord.st + vec2(-0.5, 0.5) * tx).rgb;
+
+	vec3 color =
+		(a + c + g + i) * 0.03125 +
+		(b + d + f + h) * 0.0625 +
+		(e + j + k + l + m) * 0.125;
+
+	gl_FragColor = max(vec4(color, 1.0), 1e-4);
+}

client/shaders/bloom_downsample/opengl_vertex.glsl

@@ -0,0 +1,11 @@
+#ifdef GL_ES
+varying mediump vec2 varTexCoord;
+#else
+centroid varying vec2 varTexCoord;
+#endif
+
+void main(void)
+{
+	varTexCoord.st = inTexCoord0.st;
+	gl_Position = inVertexPosition;
+}

client/shaders/bloom_upsample/opengl_fragment.glsl

@@ -0,0 +1,35 @@
+#define current texture0
+#define previous texture1
+
+uniform sampler2D current;
+uniform sampler2D previous;
+uniform vec2 texelSize0;
+uniform mediump float bloomRadius;
+
+#ifdef GL_ES
+varying mediump vec2 varTexCoord;
+#else
+centroid varying vec2 varTexCoord;
+#endif
+
+void main(void)
+{
+	vec2 offset = bloomRadius * texelSize0;
+
+	vec3 a = texture2D(previous, varTexCoord.st + vec2(-1., -1.) * offset).rgb;
+	vec3 b = texture2D(previous, varTexCoord.st + vec2(0., -1.) * offset).rgb;
+	vec3 c = texture2D(previous, varTexCoord.st + vec2(1., -1.) * offset).rgb;
+	vec3 d = texture2D(previous, varTexCoord.st + vec2(-1., 0.) * offset).rgb;
+	vec3 e = texture2D(previous, varTexCoord.st + vec2(0., 0.) * offset).rgb;
+	vec3 f = texture2D(previous, varTexCoord.st + vec2(1., 0.) * offset).rgb;
+	vec3 g = texture2D(previous, varTexCoord.st + vec2(-1., 1.) * offset).rgb;
+	vec3 h = texture2D(previous, varTexCoord.st + vec2(0., 1.) * offset).rgb;
+	vec3 i = texture2D(previous, varTexCoord.st + vec2(1., 1.) * offset).rgb;
+
+	vec3 base = texture2D(current, varTexCoord.st).rgb;
+
+	gl_FragColor = max(vec4(base +
+			(a + c + g + i) * 0.0625 +
+			(b + d + f + h) * 0.125 +
+			e * 0.25, 1.), 1e-4);
+}

client/shaders/bloom_upsample/opengl_vertex.glsl

@@ -0,0 +1,11 @@
+#ifdef GL_ES
+varying mediump vec2 varTexCoord;
+#else
+centroid varying vec2 varTexCoord;
+#endif
+
+void main(void)
+{
+	varTexCoord.st = inTexCoord0.st;
+	gl_Position = inVertexPosition;
+}

client/shaders/blur_h/opengl_fragment.glsl

@@ -3,6 +3,7 @@
 uniform sampler2D rendered;
 uniform vec2 texelSize0;
 uniform mediump float bloomRadius;
+uniform mat3 bloomBlurWeights;
 
 #ifdef GL_ES
 varying mediump vec2 varTexCoord;
@@ -10,6 +11,13 @@ varying mediump vec2 varTexCoord;
 centroid varying vec2 varTexCoord;
 #endif
 
+// smoothstep - squared
+float smstsq(float f)
+{
+	f = f * f * (3 - 2 * f);
+	return f;
+}
+
 void main(void)
 {
 	// kernel distance and linear size
@@ -19,8 +27,8 @@ void main(void)
 	vec4 color = vec4(0.);
 	mediump float sum = 0.;
 	for (mediump float i = 0.; i < n; i++) {
-		mediump float weight = pow(1. - (abs(i / bloomRadius - 1.)), 1.3);
-		color += texture2D(rendered, uv).rgba * weight;
+		mediump float weight = smstsq(1. - (abs(i / bloomRadius - 1.)));
+		color.rgb += texture2D(rendered, uv).rgb * weight;
 		sum += weight;
 		uv += vec2(texelSize0.x, 0.);
 	}

client/shaders/blur_v/opengl_fragment.glsl

@@ -3,6 +3,7 @@
 uniform sampler2D rendered;
 uniform vec2 texelSize0;
 uniform mediump float bloomRadius;
+uniform mat3 bloomBlurWeights;
 
 #ifdef GL_ES
 varying mediump vec2 varTexCoord;
@@ -10,6 +11,13 @@ varying mediump vec2 varTexCoord;
 centroid varying vec2 varTexCoord;
 #endif
 
+// smoothstep - squared
+float smstsq(float f)
+{
+	f = f * f * (3 - 2 * f);
+	return f;
+}
+
 void main(void)
 {
 	// kernel distance and linear size
@@ -19,8 +27,8 @@ void main(void)
 	vec4 color = vec4(0.);
 	mediump float sum = 0.;
 	for (mediump float i = 0.; i < n; i++) {
-		mediump float weight = pow(1. - (abs(i / bloomRadius - 1.)), 1.3);
-		color += texture2D(rendered, uv).rgba * weight;
+		mediump float weight = smstsq(1. - (abs(i / bloomRadius - 1.)));
+		color.rgb += texture2D(rendered, uv).rgb * weight;
 		sum += weight;
 		uv += vec2(0., texelSize0.y);
 	}

client/shaders/extract_bloom/opengl_fragment.glsl

@@ -2,7 +2,7 @@
 
 uniform sampler2D rendered;
 uniform mediump float exposureFactor;
-uniform float bloomLuminanceThreshold;
+uniform mediump float bloomStrength;
 
 #ifdef GL_ES
 varying mediump vec2 varTexCoord;
@@ -14,8 +14,14 @@ centroid varying vec2 varTexCoord;
 void main(void)
 {
 	vec2 uv = varTexCoord.st;
-	vec4 color = texture2D(rendered, uv).rgba;
+	vec3 color = texture2D(rendered, uv).rgb;
 	// translate to linear colorspace (approximate)
-	color.rgb = pow(color.rgb, vec3(2.2)) * exposureFactor;
-	gl_FragColor = vec4(color.rgb, 1.0); // force full alpha to avoid holes in the image.
+	color = pow(color, vec3(2.2));
+
+	// Scale colors by luminance to amplify bright colors
+	// in SDR textures.
+	float luminance = dot(color, vec3(0.213, 0.515, 0.072));
+	luminance *= luminance;
+	color *= luminance * exposureFactor * bloomStrength;
+	gl_FragColor = vec4(color, 1.0); // force full alpha to avoid holes in the image.
 }

client/shaders/second_stage/opengl_fragment.glsl

@@ -16,15 +16,14 @@ centroid varying vec2 varTexCoord;
 
 vec4 applyBloom(vec4 color, vec2 uv)
 {
-	float bias = bloomIntensity;
-	vec4 bloom = texture2D(bloom, uv);
+	vec3 light = texture2D(bloom, uv).rgb;
 #ifdef ENABLE_BLOOM_DEBUG
 	if (uv.x > 0.5 && uv.y < 0.5)
-		return vec4(bloom.rgb, color.a);
+		return vec4(light, color.a);
 	if (uv.x < 0.5)
-		return color;
+		return light;
 #endif
-	color.rgb = mix(color.rgb, bloom.rgb, bias);
+	color.rgb = mix(color.rgb, light, bloomIntensity);
 	return color;
 }
 
@@ -86,8 +85,6 @@ void main(void)
 	{
 #if ENABLE_TONE_MAPPING
 		color = applyToneMapping(color);
-#else
-		color.rgb /= 2.5; // default exposure factor, see also RenderingEngine::DEFAULT_EXPOSURE_FACTOR;
 #endif
 	}