summaryrefslogtreecommitdiffstatshomepage
path: root/3rdparty/bgfx/examples/40-svt/virtualtexture.sh
diff options
context:
space:
mode:
Diffstat (limited to '3rdparty/bgfx/examples/40-svt/virtualtexture.sh')
-rw-r--r--3rdparty/bgfx/examples/40-svt/virtualtexture.sh86
1 files changed, 86 insertions, 0 deletions
diff --git a/3rdparty/bgfx/examples/40-svt/virtualtexture.sh b/3rdparty/bgfx/examples/40-svt/virtualtexture.sh
new file mode 100644
index 00000000000..7bf584c7ed1
--- /dev/null
+++ b/3rdparty/bgfx/examples/40-svt/virtualtexture.sh
@@ -0,0 +1,86 @@
+/*
+ * Copyright 2011-2019 Branimir Karadzic. All rights reserved.
+ * License: https://github.com/bkaradzic/bgfx#license-bsd-2-clause
+ */
+
+/*
+ * Reference(s):
+ * - Based on Virtual Texture Demo by Brad Blanchard
+ * http://web.archive.org/web/20190103162638/http://linedef.com/virtual-texture-demo.html
+ */
+
+uniform vec4 u_vt_settings_1;
+uniform vec4 u_vt_settings_2;
+
+#define VirtualTextureSize u_vt_settings_1.x
+#define AtlasScale u_vt_settings_1.y
+#define BorderScale u_vt_settings_1.z
+#define BorderOffset u_vt_settings_1.w
+
+#define MipBias u_vt_settings_2.x
+#define PageTableSize u_vt_settings_2.y
+
+SAMPLER2D(s_vt_page_table, 0);
+SAMPLER2D(s_vt_texture_atlas, 1);
+
+// This function estimates mipmap levels
+float MipLevel( vec2 uv, float size )
+{
+ vec2 dx = dFdx( uv * size );
+ vec2 dy = dFdy( uv * size );
+ float d = max( dot( dx, dx ), dot( dy, dy ) );
+
+ return max( 0.5 * log2( d ), 0 );
+}
+
+// This function samples the page table and returns the page's
+// position and mip level.
+vec3 SampleTable( vec2 uv, float mip )
+{
+ vec2 offset = fract( uv * PageTableSize ) / PageTableSize;
+ return texture2DLod( s_vt_page_table, uv - offset, mip ).xyz;
+}
+
+// This functions samples from the texture atlas and returns the final color
+vec4 SampleAtlas( vec3 page, vec2 uv )
+{
+ float mipsize = exp2( floor( page.z * 255.0 + 0.5 ) );
+
+ uv = fract( uv * PageTableSize / mipsize );
+
+ uv *= BorderScale;
+ uv += BorderOffset;
+
+ vec2 offset = floor( page.xy * 255.0 + 0.5 );
+
+ return texture2D( s_vt_texture_atlas, ( offset + uv ) * AtlasScale );
+}
+
+// Ugly brute force trilinear, look up twice and mix
+vec4 VirtualTextureTrilinear( vec2 uv )
+{
+ float miplevel = MipLevel( uv, VirtualTextureSize );
+ miplevel = clamp( miplevel, 0.0, log2( PageTableSize )-1.0 );
+
+ float mip1 = floor( miplevel );
+ float mip2 = mip1 + 1.0;
+ float mipfrac = miplevel - mip1;
+
+ vec3 page1 = SampleTable( uv, mip1 );
+ vec3 page2 = SampleTable( uv, mip2 );
+
+ vec4 sample1 = SampleAtlas( page1, uv );
+ vec4 sample2 = SampleAtlas( page2, uv );
+
+ return mix( sample1, sample2, mipfrac );
+}
+
+// Simple bilinear
+vec4 VirtualTexture( vec2 uv )
+{
+ float mip = floor( MipLevel( uv, VirtualTextureSize ) );
+ mip = clamp( mip, 0, log2( PageTableSize ) );
+
+ vec3 page = SampleTable( uv, mip );
+ return SampleAtlas( page, uv );
+}