Add iDate builtin to Shadertoy utility (#428)

* Add iDate to glsl builtins

* add iDate to wgsl builtins

* Fix memory offset error

* Fix order of fields in Uniform array

* Fix style

* Add example for iDate

* Replace tabs with spaces

---------

Co-authored-by: Korijn van Golen <[email protected]>

examples/shadertoy_glsl_clock.py

@@ -0,0 +1,94 @@
+from wgpu.utils.shadertoy import Shadertoy
+
+shader_code = """
+// source: https://www.shadertoy.com/view/MdVcRd
+
+// See https://www.shadertoy.com/view/ldKGRR
+
+// Computes a smooth-edged diamond pixel value (Manhattan distance)
+#define P(i, j, b) \
+    vec2(.1, b).xyxy * smoothstep(0., 9. / R.y, .1 - abs(i) - abs(j))
+
+// Computes a segment value (length = 0.5)
+#define S(i, j, b) \
+    P(i - clamp(i, 0., .5), j, b & 1)
+
+// Colon render
+#define C \
+    x += .5; O += P(x, y + .3, i.w / 50) + P(x, y - .3, i.w / 50); t /= 60
+
+// Hyphen render
+#define H(b) \
+    ++x; O += S(x, y, b)
+
+// Computes the horizontal and vertical segments based on a denary digit
+#define X(i, j, b) \
+    S(x - i, y - j, b)
+#define Y(i, j, b) \
+    S(y - j, x - i, b)
+#define D(n) \
+    H(892>>n) \
+    + X(0., .7, 1005>>n) \
+    + X(0., -.7, 877>>n) \
+    + Y(-.1, .1, 881>>n) \
+    + Y(.6, .1, 927>>n) \
+    + Y(-.1, -.6, 325>>n) \
+    + Y(.6, -.6, 1019>>n);
+
+// Two-digit render
+#define Z(n) ; D(n % 10) D(n / 10)
+
+void mainImage(out vec4 O, vec2 U)
+{
+    vec2 R = iResolution.xy;
+    U += U - R;
+    U /= R.y / 3.; // Global scaling with aspect ratio correction
+    O-=O; // Zero the pixel
+
+    float x = U.x - U.y * .2 - 2.8, // Slight skew to slant the digits
+          y = --U.y;
+    ivec4 i = ivec4(iDate); // Convert everything to integers
+    int t = i.w;
+    i.w = int(iDate.w * 100.) % 100 // Replace with centiseconds
+    
+    // Seconds (preceded by a colon)
+    Z(t % 60)
+    C
+    
+    // Minutes (preceded by a colon)
+    Z(t % 60)
+    C
+    
+    // Hours
+    Z(t)
+
+    // Smaller digits
+    x /= .6;
+    y /= .6;
+    R *= .6;
+
+    // Centiseconds
+    x -= 14.;
+    y += .53
+    Z(i.w)
+
+    // Day (preceded by a hyphen)
+    x -= .8;
+    y += 3.
+    Z(i.z)
+    H(1)
+
+    // Month (preceded by a hyphen)
+    Z((i.y + 1)) // Is it a bug in shadertoy that we have to add one?
+    H(1)
+
+    // Year
+    Z(i.x % 100)
+    Z(i.x / 100)
+}
+
+"""  # noqa
+shader = Shadertoy(shader_code)
+
+if __name__ == "__main__":
+    shader.show()

wgpu/utils/shadertoy.py

@@ -29,18 +29,20 @@
 builtin_variables_glsl = """
 #version 450 core
 
-vec3 i_resolution;
 vec4 i_mouse;
+vec4 i_date;
+vec3 i_resolution;
 float i_time;
 float i_time_delta;
 int i_frame;
 
 // Shadertoy compatibility, see we can use the same code copied from shadertoy website
 
-#define iTime i_time
+#define iMouse i_mouse
+#define iDate i_date
 #define iResolution i_resolution
+#define iTime i_time
 #define iTimeDelta i_time_delta
-#define iMouse i_mouse
 #define iFrame i_frame
 
 #define mainImage shader_main
@@ -52,6 +54,7 @@
 
 struct ShadertoyInput {
     vec4 mouse;
+    vec4 date;
     vec3 resolution;
     float time;
     float time_delta;
@@ -62,13 +65,13 @@
 out vec4 FragColor;
 void main(){
 
-    i_time = input.time;
+    i_mouse = input.mouse;
+    i_date = input.date;
     i_resolution = input.resolution;
+    i_time = input.time;
     i_time_delta = input.time_delta;
-    i_mouse = input.mouse;
     i_frame = input.frame;
 
-
     vec2 uv = vec2(uv.x, 1.0 - uv.y);
     vec2 frag_coord = uv * i_resolution.xy;
 
@@ -107,8 +110,9 @@
 
 builtin_variables_wgsl = """
 
-var<private> i_resolution: vec3<f32>;
 var<private> i_mouse: vec4<f32>;
+var<private> i_date: vec4<f32>;
+var<private> i_resolution: vec3<f32>;
 var<private> i_time_delta: f32;
 var<private> i_time: f32;
 var<private> i_frame: u32;
@@ -123,6 +127,7 @@
 
 struct ShadertoyInput {
     mouse: vec4<f32>,
+    date: vec4<f32>,
     resolution: vec3<f32>,
     time: f32,
     time_delta: f32,
@@ -141,10 +146,11 @@
 @fragment
 fn main(in: Varyings) -> @location(0) vec4<f32> {
 
-    i_time = input.time;
+    i_mouse = input.mouse;
+    i_date = input.date;
     i_resolution = input.resolution;
+    i_time = input.time;
     i_time_delta = input.time_delta;
-    i_mouse = input.mouse;
     i_frame = input.frame;
 
 
@@ -169,6 +175,8 @@ class UniformArray:
     """Convenience class to create a uniform array.
 
     Maybe we can make it a public util at some point.
+    Ensure that the order matches structs in the shader code.
+    See https://www.w3.org/TR/WGSL/#alignment-and-size for reference on alignment.
     """
 
     def __init__(self, *args):
@@ -239,8 +247,9 @@ class Shadertoy:
     * ``i_frame``: the frame number
     * ``i_resolution``: the resolution of the shadertoy
     * ``i_mouse``: the mouse position in pixels
+    * ``i_date``: the current date and time as a vec4 (year, month, day, seconds)
 
-    For GLSL, you can also use the aliases ``iTime``, ``iTimeDelta``, ``iFrame``, ``iResolution``, and ``iMouse`` of these built-in variables,
+    For GLSL, you can also use the aliases ``iTime``, ``iTimeDelta``, ``iFrame``, ``iResolution``, ``iMouse`` and ``iDate`` of these built-in variables,
     the entry point function also has an alias ``mainImage``, so you can use the shader code copied from shadertoy website without making any changes.
     """
 
@@ -251,6 +260,7 @@ class Shadertoy:
     def __init__(self, shader_code, resolution=(800, 450), offscreen=False) -> None:
         self._uniform_data = UniformArray(
             ("mouse", "f", 4),
+            ("date", "f", 4),
             ("resolution", "f", 3),
             ("time", "f", 1),
             ("time_delta", "f", 1),
@@ -429,6 +439,17 @@ def _update(self):
         if not hasattr(self, "_frame"):
             self._frame = 0
 
+        time_struct = time.localtime()
+        self._uniform_data["date"] = (
+            float(time_struct.tm_year),
+            float(time_struct.tm_mon - 1),
+            float(time_struct.tm_mday),
+            time_struct.tm_hour * 3600
+            + time_struct.tm_min * 60
+            + time_struct.tm_sec
+            + now % 1,
+        )
+
         self._uniform_data["frame"] = self._frame
         self._frame += 1