adding point rasterization

build.zig.zon

@@ -32,8 +32,8 @@
 
         // Soft dependencies
         .SPIRV_Interpreter = .{
-            .url = "git+https://git.kbz8.me/kbz_8/SPIRV-Interpreter#42554a5cc1069e8174b377e95ce2ac2d802a44ff",
-            .hash = "SPIRV_Interpreter-0.0.1-ajmpn0GXBwD01BnmV_Kf8EeNqTDoyuq7UvHVaq-WoBP0",
+            .url = "git+https://github.com/Kbz-8/SPIRV-Interpreter#391f4415d9a77d15455f4d7efab65fc8cc931bc5",
+            .hash = "SPIRV_Interpreter-0.0.1-ajmpn6mrBwDO21UuGIRs3iP-0Z9GyhivF3N8V_X4tLzX",
             .lazy = true,
         },
         //.SPIRV_Interpreter = .{

src/software/device/Renderer.zig

@@ -55,6 +55,7 @@ pub const DynamicState = struct {
 pub const Vertex = struct {
     primitive_restart: bool,
     position: F32x4,
+    point_size: f32,
     outputs: [spv.SPIRV_MAX_OUTPUT_LOCATIONS][4]?struct {
         interpolation_type: enum { smooth, flat, noperspective },
         blob: []u8,
@@ -106,6 +107,7 @@ pub const DrawCall = struct {
 
         for (self.vertices) |*vertex| {
             vertex.primitive_restart = false;
+            vertex.point_size = 1.0;
             for (&vertex.outputs) |*location| {
                 @memset(location, null);
             }

src/software/device/clip.zig

@@ -171,6 +171,7 @@ fn interpolateVertexForClipping(allocator: std.mem.Allocator, a: *const Vertex,
     var result: Vertex = .{
         .primitive_restart = false,
         .position = a.position + ((b.position - a.position) * zm.f32x4s(t)),
+        .point_size = a.point_size + ((b.point_size - a.point_size) * t),
         .outputs = undefined,
     };
 

src/software/device/fragment.zig

@@ -23,6 +23,7 @@ pub fn shaderInvocation(
     draw_call: *Renderer.DrawCall,
     batch_id: usize,
     position: zm.F32x4,
+    point_coord: ?@Vector(2, f32),
     front_face: bool,
     inputs: [spv.SPIRV_MAX_OUTPUT_LOCATIONS]VertexInterpolationLocation,
     derivative_inputs: ?DerivativeInputs,
@@ -54,6 +55,12 @@ pub fn shaderInvocation(
         SpvRuntimeError.NotFound => {},
         else => return err,
     };
+    if (point_coord) |coord| {
+        rt.writeBuiltIn(std.mem.asBytes(&coord), .PointCoord) catch |err| switch (err) {
+            SpvRuntimeError.NotFound => {},
+            else => return err,
+        };
+    }
     rt.writeBuiltIn(std.mem.asBytes(&front_face), .FrontFacing) catch |err| switch (err) {
         SpvRuntimeError.NotFound => {},
         else => return err,

src/software/device/rasterizer.zig

@@ -323,11 +323,13 @@ fn clipTransformAndRasterizePoint(
     var transformed = vertex.*;
     clip.viewportTransformVertex(draw_call.viewport, &transformed);
 
-    const point_size = 1.0;
+    const point_size = transformed.point_size;
     const min_x: i32 = @intFromFloat(@ceil(transformed.position[0] - (point_size / 2.0) - 0.5));
     const max_x: i32 = @intFromFloat(@ceil(transformed.position[0] + (point_size / 2.0) - 0.5) - 1.0);
     const min_y: i32 = @intFromFloat(@ceil(transformed.position[1] - (point_size / 2.0) - 0.5));
     const max_y: i32 = @intFromFloat(@ceil(transformed.position[1] + (point_size / 2.0) - 0.5) - 1.0);
+    const point_min_x = transformed.position[0] - (point_size / 2.0);
+    const point_min_y = transformed.position[1] - (point_size / 2.0);
     const pipeline = draw_call.renderer.state.pipeline orelse return;
     const has_fragment_shader = pipeline.stages.getPtr(.fragment) != null;
 
@@ -340,11 +342,19 @@ fn clipTransformAndRasterizePoint(
 
             var outputs = std.mem.zeroes([spv.SPIRV_MAX_OUTPUT_LOCATIONS][@sizeOf(zm.F32x4)]u8);
             if (has_fragment_shader) {
+                const frag_x = @as(f32, @floatFromInt(px)) + 0.5;
+                const frag_y = @as(f32, @floatFromInt(py)) + 0.5;
+                const point_coord = @Vector(2, f32){
+                    (frag_x - point_min_x) / point_size,
+                    (frag_y - point_min_y) / point_size,
+                };
+
                 outputs = fragment.shaderInvocation(
                     allocator,
                     draw_call,
                     0,
-                    zm.f32x4(@floatFromInt(px), @floatFromInt(py), transformed.position[2], 1.0),
+                    zm.f32x4(frag_x, frag_y, transformed.position[2], 1.0 / transformed.position[3]),
+                    point_coord,
                     true,
                     try common.interpolateVertexOutputs(allocator, &transformed, &transformed, &transformed, 1.0, 0.0, 0.0),
                     null,

src/software/device/rasterizer/bresenham.zig

@@ -45,9 +45,9 @@ pub fn drawLine(
     const io = draw_call.renderer.device.interface.io();
 
     var x0: i32 = @intFromFloat(v0.position[0]);
-    var y0: i32 = @intFromFloat(v0.position[1]);
+    var y0: i32 = @intFromFloat(@floor(v0.position[1] - 0.5));
     var x1: i32 = @intFromFloat(v1.position[0]);
-    var y1: i32 = @intFromFloat(v1.position[1]);
+    var y1: i32 = @intFromFloat(@floor(v1.position[1] - 0.5));
 
     const steep = blk: {
         if (@abs(y1 - y0) > @abs(x1 - x0)) {
@@ -76,7 +76,7 @@ pub fn drawLine(
     if (runtimes_count == 0)
         return;
 
-    const step_count: usize = @as(usize, @intCast(d_x)) + 1;
+    const step_count: usize = if (d_x == 0) 1 else @intCast(d_x);
     const runs_count = @min(runtimes_count, step_count);
     const steps_per_run = @divTrunc(step_count + runs_count - 1, runs_count);
 
@@ -151,6 +151,7 @@ inline fn run(data: RunData) !void {
 
         const t = @as(f32, @floatFromInt(step)) / @as(f32, @floatFromInt(@max(data.d_x, 1)));
         const z = ((1.0 - t) * data.start_vertex.position[2]) + (t * data.end_vertex.position[2]);
+        const frag_w = ((1.0 - t) / data.start_vertex.position[3]) + (t / data.end_vertex.position[3]);
 
         var outputs = std.mem.zeroes([spv.SPIRV_MAX_OUTPUT_LOCATIONS][@sizeOf(F32x4)]u8);
         if (data.has_fragment_shader) {
@@ -158,7 +159,8 @@ inline fn run(data: RunData) !void {
                 data.allocator,
                 data.draw_call,
                 data.batch_id,
-                zm.f32x4(@floatFromInt(pixel_x), @floatFromInt(pixel_y), z, 1.0),
+                zm.f32x4(@as(f32, @floatFromInt(pixel_x)) + 0.5, @as(f32, @floatFromInt(pixel_y)) + 0.5, z, frag_w),
+                null,
                 true,
                 try common.interpolateLineOutputs(data.allocator, data.start_vertex, data.end_vertex, t),
                 null,

src/software/device/rasterizer/edge_function.zig

@@ -177,6 +177,7 @@ inline fn run(data: RunData) !void {
             const b1 = w1 / data.area;
             const b2 = w2 / data.area;
             const z = (b0 * data.v0.position[2]) + (b1 * data.v1.position[2]) + (b2 * data.v2.position[2]);
+            const frag_w = (b0 / data.v0.position[3]) + (b1 / data.v1.position[3]) + (b2 / data.v2.position[3]);
 
             var outputs = std.mem.zeroes([spv.SPIRV_MAX_OUTPUT_LOCATIONS][@sizeOf(F32x4)]u8);
             if (data.has_fragment_shader) {
@@ -218,7 +219,8 @@ inline fn run(data: RunData) !void {
                     data.allocator,
                     data.draw_call,
                     data.batch_id,
-                    zm.f32x4(@floatFromInt(x), @floatFromInt(y), z, 1.0),
+                    zm.f32x4(@as(f32, @floatFromInt(x)) + 0.5, @as(f32, @floatFromInt(y)) + 0.5, z, frag_w),
+                    null,
                     data.front_face,
                     inputs,
                     derivative_inputs,

src/software/device/vertex_dispatcher.zig

@@ -107,6 +107,7 @@ inline fn run(data: RunData) !void {
         };
 
         try readPosition(rt, std.mem.asBytes(&output.position));
+        try readPointSize(rt, &output.point_size);
 
         for (0..spv.SPIRV_MAX_OUTPUT_LOCATIONS) |location| {
             for (0..4) |component| {
@@ -187,6 +188,15 @@ fn readPosition(rt: *spv.Runtime, output: []u8) !void {
     return SpvRuntimeError.InvalidSpirV;
 }
 
+fn readPointSize(rt: *spv.Runtime, output: *f32) !void {
+    if (rt.readBuiltIn(std.mem.asBytes(output), .PointSize)) {
+        return;
+    } else |err| switch (err) {
+        SpvRuntimeError.InvalidSpirV, SpvRuntimeError.NotFound => {},
+        else => return err,
+    }
+}
+
 fn isConstantZero(rt: *spv.Runtime, result_word: spv.SpvWord) bool {
     if (result_word >= rt.results.len)
         return false;