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Diffstat (limited to 'src/sksl/README')
| -rw-r--r-- | src/sksl/README | 24 |
1 files changed, 11 insertions, 13 deletions
diff --git a/src/sksl/README b/src/sksl/README index f590bbeae2..012895412e 100644 --- a/src/sksl/README +++ b/src/sksl/README @@ -13,12 +13,10 @@ before handing it over to the graphics driver. Differences from GLSL ===================== -SkSL is based on GLSL 4.5. For the most part, write SkSL exactly as you would -desktop GLSL, and the SkSL compiler will take care of version and dialect -differences (for instance, you always use "in" and "out", and skslc will handle -translating them to "varying" and "attribute" as appropriate). Be aware of the -following differences between SkSL and GLSL: - +* Vector types are named <base type><columns>, so float2 instead of vec2 and + bool4 instead of bvec4 +* Matrix types are named <base type><columns>x<rows>, so float2x3 instead of + mat2x3 and double4x4 instead of dmat4 * "@if" and "@switch" are static versions of if and switch. They behave exactly the same as if and switch in all respects other than it being a compile-time error to use a non-constant expression as a test. @@ -35,7 +33,7 @@ following differences between SkSL and GLSL: will compile as if you had written either 'do_something();' or 'do_something_else();', depending on whether that cap is enabled or not. -* no #version statement is required, and will be ignored if present +* no #version statement is required, and it will be ignored if present * the output color is sk_FragColor (do not declare it) * use sk_VertexID instead of gl_VertexID * the fragment coordinate is sk_FragCoord, and is always relative to the upper @@ -43,15 +41,15 @@ following differences between SkSL and GLSL: * lowp, mediump, and highp are always permitted (but will only be respected if you run on a device which supports them) * you do not need to include ".0" to make a number a float (meaning that - "vec2(x, y) * 4" is perfectly legal in SkSL, unlike GLSL where it would often - have to be expressed "vec2(x, y) * 4.0". There is no performance penalty for + "float2x, y) * 4" is perfectly legal in SkSL, unlike GLSL where it would often + have to be expressed "float2x, y) * 4.0". There is no performance penalty for this, as the number is converted to a float at compile time) * type suffixes on numbers (1.0f, 0xFFu) are both unnecessary and unsupported -* creating a smaller vector from a larger vector (e.g. vec2(vec3(1))) is +* creating a smaller vector from a larger vector (e.g. float2float31))) is intentionally disallowed, as it is just a wordier way of performing a swizzle. Use swizzles instead. -* Use texture() instead of textureProj(), e.g. texture(sampler2D, vec3) is - equivalent to GLSL's textureProj(sampler2D, vec3) +* Use texture() instead of textureProj(), e.g. texture(sampler2D, float3 is + equivalent to GLSL's textureProj(sampler2D, float3 * some built-in functions and one or two rarely-used language features are not yet supported (sorry!) @@ -96,7 +94,7 @@ Within an '.fp' fragment processor file: (the sampler params to attach to the named sampler2D) * global 'in' variables represent data passed to the fragment processor at construction time. These variables become constructor parameters and are - stored in fragment processor fields. vec2s map to SkPoints, and vec4s map to + stored in fragment processor fields. float2 map to SkPoints, and float4 map to SkRects (in x, y, width, height) order. * 'uniform' variables become, as one would expect, top-level uniforms. By default they do not have any data provided to them; you will need to provide |