internal/shader: add refract

Closes #2255

internal/shader/expr.go

@@ -447,7 +447,7 @@ func (cs *compileState) parseExpr(block *block, fname string, expr ast.Expr, mar
 				})
 				return nil, nil, stmts, true
 
-			case shaderir.Clamp, shaderir.Mix, shaderir.Smoothstep, shaderir.Faceforward:
+			case shaderir.Clamp, shaderir.Mix, shaderir.Smoothstep, shaderir.Faceforward, shaderir.Refract:
 				// 3 arguments
 				if len(args) != 3 {
 					cs.addError(e.Pos(), fmt.Sprintf("number of %s's arguments must be 3 but %d", callee.BuiltinFunc, len(args)))
@@ -485,6 +485,15 @@ func (cs *compileState) parseExpr(block *block, fname string, expr ast.Expr, mar
 						cs.addError(e.Pos(), fmt.Sprintf("the first and the second arguments for %s must equal to the third argument %s or float but %s and %s", callee.BuiltinFunc, argts[2].String(), argts[0].String(), argts[1].String()))
 						return nil, nil, nil, false
 					}
+				case shaderir.Refract:
+					if !argts[0].Equal(&argts[1]) {
+						cs.addError(e.Pos(), fmt.Sprintf("%s and %s don't match in argument to %s", argts[0].String(), argts[1].String(), callee.BuiltinFunc))
+						return nil, nil, nil, false
+					}
+					if argts[2].Main != shaderir.Float {
+						cs.addError(e.Pos(), fmt.Sprintf("cannot use %s as float value in argument to %s", argts[2].String(), callee.BuiltinFunc))
+						return nil, nil, nil, false
+					}
 				default:
 					if !argts[0].Equal(&argts[1]) || !argts[0].Equal(&argts[2]) {
 						cs.addError(e.Pos(), fmt.Sprintf("all the argument types for %s must be the same but %s, %s, and %s", callee.BuiltinFunc, argts[0].String(), argts[1].String(), argts[2].String()))

internal/shader/syntax_test.go

@@ -2053,6 +2053,57 @@ func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
 	}
 }
 
+// Issue #2184
+func TestSyntaxBuiltinFuncRefractType(t *testing.T) {
+	cases := []struct {
+		stmt string
+		err  bool
+	}{
+		{stmt: "a := refract(); _ = a", err: true},
+		{stmt: "a := refract(1); _ = a", err: true},
+		{stmt: "a := refract(false, false); _ = a", err: true},
+		{stmt: "a := refract(1, 1); _ = a", err: true},
+		{stmt: "a := refract(false, false, false); _ = a", err: true},
+		{stmt: "a := refract(1, 1, 1); _ = a", err: false},
+		{stmt: "a := refract(1.0, 1, 1); _ = a", err: false},
+		{stmt: "a := refract(1, 1.0, 1); _ = a", err: false},
+		{stmt: "a := refract(1, 1, 1.0); _ = a", err: false},
+		{stmt: "a := refract(1, vec2(1), 1); _ = a", err: true},
+		{stmt: "a := refract(1, 1, vec2(1)); _ = a", err: true},
+		{stmt: "a := refract(1, vec2(1), vec2(1)); _ = a", err: true},
+		{stmt: "a := refract(vec2(1), 1, 1); _ = a", err: true},
+		{stmt: "a := refract(vec2(1), 1, vec2(1)); _ = a", err: true},
+		{stmt: "a := refract(vec2(1), vec2(1), 1); _ = a", err: false}, // The third argument must be a float.
+		{stmt: "a := refract(vec2(1), vec2(1), vec2(1)); _ = a", err: true},
+		{stmt: "a := refract(vec2(1), vec2(1), vec3(1)); _ = a", err: true},
+		{stmt: "a := refract(vec3(1), 1, 1); _ = a", err: true},
+		{stmt: "a := refract(vec3(1), 1, vec3(1)); _ = a", err: true},
+		{stmt: "a := refract(vec3(1), vec3(1), 1); _ = a", err: false}, // The third argument must be a float.
+		{stmt: "a := refract(vec3(1), vec3(1), vec3(1)); _ = a", err: true},
+		{stmt: "a := refract(vec4(1), 1, 1); _ = a", err: true},
+		{stmt: "a := refract(vec4(1), 1, vec4(1)); _ = a", err: true},
+		{stmt: "a := refract(vec4(1), vec4(1), 1); _ = a", err: false}, // The third argument must be a float.
+		{stmt: "a := refract(vec4(1), vec4(1), vec4(1)); _ = a", err: true},
+		{stmt: "a := refract(1, 1, 1, 1); _ = a", err: true},
+	}
+
+	for _, c := range cases {
+		stmt := c.stmt
+		src := fmt.Sprintf(`package main
+
+func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
+	%s
+	return position
+}`, stmt)
+		_, err := compileToIR([]byte(src))
+		if err == nil && c.err {
+			t.Errorf("%s must return an error but does not", stmt)
+		} else if err != nil && !c.err {
+			t.Errorf("%s must not return nil but returned %v", stmt, err)
+		}
+	}
+}
+
 // Issue #2184
 func TestSyntaxBuiltinFuncCrossType(t *testing.T) {
 	cases := []struct {

internal/shaderir/program.go

@@ -259,6 +259,7 @@ const (
 	Normalize   BuiltinFunc = "normalize"
 	Faceforward BuiltinFunc = "faceforward"
 	Reflect     BuiltinFunc = "reflect"
+	Refract     BuiltinFunc = "refract"
 	Transpose   BuiltinFunc = "transpose"
 	Texture2DF  BuiltinFunc = "texture2D"
 	Dfdx        BuiltinFunc = "dfdx"
@@ -313,6 +314,7 @@ func ParseBuiltinFunc(str string) (BuiltinFunc, bool) {
 		Normalize,
 		Faceforward,
 		Reflect,
+		Refract,
 		Transpose,
 		Texture2DF,
 		Dfdx,