add all

3 files changed, 430 insertions, 0 deletions

diff --git a/src/main.zig b/src/main.zig
new file mode 100644
index 0000000..4c6d98a
--- /dev/null
+++ b/src/main.zig
@@ -0,0 +1,107 @@
+//------------------------------------------------------------------------------
+//  offscreen.zig
+//
+//  Render to an offscreen rendertarget texture, and use this texture
+//  for rendering to the display.
+//------------------------------------------------------------------------------
+const sokol = @import("sokol");
+const slog = sokol.log;
+const sg = sokol.gfx;
+const sapp = sokol.app;
+const sglue = sokol.glue;
+const imgui = sokol.imgui;
+const appimgui = sokol.appimgui;
+const vec3 = @import("math.zig").Vec3;
+const mat4 = @import("math.zig").Mat4;
+const shd = @import("shaders/main.glsl.zig");
+
+const state = struct {
+    const display = struct {
+        var pass_action: sg.PassAction = .{};
+        var pip: sg.Pipeline = .{};
+        var bind: sg.Bindings = .{};
+    };
+};
+
+export fn init() void {
+    sg.setup(.{
+        .environment = sglue.environment(),
+        .logger = .{ .func = slog.func },
+    });
+
+    imgui.setup(.{});
+    appimgui.setup();
+
+    // default pass action: clear to blue-ish
+    state.display.pass_action.colors[0] = .{
+        .load_action = .CLEAR,
+        .clear_value = .{ .r = 0.25, .g = 0.45, .b = 0.65, .a = 1.0 },
+    };
+
+    const vbuf = sg.makeBuffer(.{});
+    state.display.bind.vertex_buffers[0] = vbuf;
+
+    // shader and pipeline object for the default render pass
+    state.display.pip = sg.makePipeline(.{
+        .shader = sg.makeShader(shd.offscreenShaderDesc(sg.queryBackend())),
+        .layout = init: {
+            var l = sg.VertexLayoutState{};
+            l.attrs[shd.ATTR_offscreen_position] = .{};
+            break :init l;
+        },
+        .index_type = .UINT16,
+        .cull_mode = .BACK,
+        .depth = .{
+            .compare = .LESS_EQUAL,
+            .write_enabled = true,
+        },
+    });
+}
+
+export fn event(ev: [*c]const sapp.Event) void {
+    appimgui.trackEvent(ev.*);
+}
+
+export fn frame() void {
+    // const dt: f32 = @floatCast(sapp.frameDuration() * 60);
+    // const aspect = sapp.widthf() / sapp.heightf();
+
+    sg.beginPass(.{ .action = state.display.pass_action, .swapchain = sglue.swapchain() });
+    sg.applyPipeline(state.display.pip);
+    sg.applyBindings(state.display.bind);
+    sg.draw(0, 3, 1);
+    sg.endPass();
+
+    sg.commit();
+}
+
+export fn cleanup() void {
+    appimgui.shutdown();
+    imgui.shutdown();
+    sg.shutdown();
+}
+
+pub fn main() void {
+    sapp.run(.{
+        .init_cb = init,
+        .frame_cb = frame,
+        .event_cb = event,
+        .cleanup_cb = cleanup,
+        .sample_count = 4,
+        .width = 800,
+        .height = 600,
+        .icon = .{ .sokol_default = true },
+        .window_title = "offscreen.zig",
+        .logger = .{ .func = slog.func },
+    });
+}
+
+fn computeVsParams(rx: f32, ry: f32, aspect: f32, eye_dist: f32) shd.VsParams {
+    const proj = mat4.persp(45, aspect, 0.01, 10);
+    const view = mat4.lookat(.{ .x = 0, .y = 0, .z = eye_dist }, vec3.zero(), vec3.up());
+    const view_proj = mat4.mul(proj, view);
+    const rxm = mat4.rotate(rx, .{ .x = 1, .y = 0, .z = 0 });
+    const rym = mat4.rotate(ry, .{ .x = 0, .y = 1, .z = 0 });
+    const model = mat4.mul(rxm, rym);
+    return shd.VsParams{ .mvp = mat4.mul(view_proj, model) };
+}
diff --git a/src/math.zig b/src/math.zig
new file mode 100644
index 0000000..6ca7c37
--- /dev/null
+++ b/src/math.zig
@@ -0,0 +1,290 @@
+//------------------------------------------------------------------------------
+//  math.zig
+//
+//  minimal vector math helper functions, just the stuff needed for
+//  the sokol-samples
+//
+//  Ported from HandmadeMath.h
+//------------------------------------------------------------------------------
+const assert = @import("std").debug.assert;
+const math = @import("std").math;
+
+fn radians(deg: f32) f32 {
+    return deg * (math.pi / 180.0);
+}
+
+pub const Vec2 = extern struct {
+    x: f32,
+    y: f32,
+
+    pub fn zero() Vec2 {
+        return Vec2{ .x = 0.0, .y = 0.0 };
+    }
+
+    pub fn new(x: f32, y: f32) Vec2 {
+        return Vec2{ .x = x, .y = y };
+    }
+};
+
+pub const Vec3 = extern struct {
+    x: f32,
+    y: f32,
+    z: f32,
+
+    pub fn zero() Vec3 {
+        return Vec3{ .x = 0.0, .y = 0.0, .z = 0.0 };
+    }
+
+    pub fn new(x: f32, y: f32, z: f32) Vec3 {
+        return Vec3{ .x = x, .y = y, .z = z };
+    }
+
+    pub fn up() Vec3 {
+        return Vec3{ .x = 0.0, .y = 1.0, .z = 0.0 };
+    }
+
+    pub fn len(v: Vec3) f32 {
+        return math.sqrt(Vec3.dot(v, v));
+    }
+
+    pub fn add(left: Vec3, right: Vec3) Vec3 {
+        return Vec3{ .x = left.x + right.x, .y = left.y + right.y, .z = left.z + right.z };
+    }
+
+    pub fn sub(left: Vec3, right: Vec3) Vec3 {
+        return Vec3{ .x = left.x - right.x, .y = left.y - right.y, .z = left.z - right.z };
+    }
+
+    pub fn mul(v: Vec3, s: f32) Vec3 {
+        return Vec3{ .x = v.x * s, .y = v.y * s, .z = v.z * s };
+    }
+
+    pub fn norm(v: Vec3) Vec3 {
+        const l = Vec3.len(v);
+        if (l != 0.0) {
+            return Vec3{ .x = v.x / l, .y = v.y / l, .z = v.z / l };
+        } else {
+            return Vec3.zero();
+        }
+    }
+
+    pub fn cross(v0: Vec3, v1: Vec3) Vec3 {
+        return Vec3{ .x = (v0.y * v1.z) - (v0.z * v1.y), .y = (v0.z * v1.x) - (v0.x * v1.z), .z = (v0.x * v1.y) - (v0.y * v1.x) };
+    }
+
+    pub fn dot(v0: Vec3, v1: Vec3) f32 {
+        return v0.x * v1.x + v0.y * v1.y + v0.z * v1.z;
+    }
+};
+
+pub const Mat4 = extern struct {
+    m: [4][4]f32,
+
+    pub fn identity() Mat4 {
+        return Mat4{
+            .m = [_][4]f32{ .{ 1.0, 0.0, 0.0, 0.0 }, .{ 0.0, 1.0, 0.0, 0.0 }, .{ 0.0, 0.0, 1.0, 0.0 }, .{ 0.0, 0.0, 0.0, 1.0 } },
+        };
+    }
+
+    pub fn zero() Mat4 {
+        return Mat4{
+            .m = [_][4]f32{ .{ 0.0, 0.0, 0.0, 0.0 }, .{ 0.0, 0.0, 0.0, 0.0 }, .{ 0.0, 0.0, 0.0, 0.0 }, .{ 0.0, 0.0, 0.0, 0.0 } },
+        };
+    }
+
+    pub fn mul(left: Mat4, right: Mat4) Mat4 {
+        var res = Mat4.zero();
+        for (0..4) |col| {
+            for (0..4) |row| {
+                res.m[col][row] = left.m[0][row] * right.m[col][0] +
+                    left.m[1][row] * right.m[col][1] +
+                    left.m[2][row] * right.m[col][2] +
+                    left.m[3][row] * right.m[col][3];
+            }
+        }
+        return res;
+    }
+
+    pub fn persp(fov: f32, aspect: f32, near: f32, far: f32) Mat4 {
+        var res = Mat4.identity();
+        const t = math.tan(fov * (math.pi / 360.0));
+        res.m[0][0] = 1.0 / t;
+        res.m[1][1] = aspect / t;
+        res.m[2][3] = -1.0;
+        res.m[2][2] = (near + far) / (near - far);
+        res.m[3][2] = (2.0 * near * far) / (near - far);
+        res.m[3][3] = 0.0;
+        return res;
+    }
+
+    pub fn lookat(eye: Vec3, center: Vec3, up: Vec3) Mat4 {
+        var res = Mat4.zero();
+
+        const f = Vec3.norm(Vec3.sub(center, eye));
+        const s = Vec3.norm(Vec3.cross(f, up));
+        const u = Vec3.cross(s, f);
+
+        res.m[0][0] = s.x;
+        res.m[0][1] = u.x;
+        res.m[0][2] = -f.x;
+
+        res.m[1][0] = s.y;
+        res.m[1][1] = u.y;
+        res.m[1][2] = -f.y;
+
+        res.m[2][0] = s.z;
+        res.m[2][1] = u.z;
+        res.m[2][2] = -f.z;
+
+        res.m[3][0] = -Vec3.dot(s, eye);
+        res.m[3][1] = -Vec3.dot(u, eye);
+        res.m[3][2] = Vec3.dot(f, eye);
+        res.m[3][3] = 1.0;
+
+        return res;
+    }
+
+    pub fn rotate(angle: f32, axis_unorm: Vec3) Mat4 {
+        var res = Mat4.identity();
+
+        const axis = Vec3.norm(axis_unorm);
+        const sin_theta = math.sin(radians(angle));
+        const cos_theta = math.cos(radians(angle));
+        const cos_value = 1.0 - cos_theta;
+
+        res.m[0][0] = (axis.x * axis.x * cos_value) + cos_theta;
+        res.m[0][1] = (axis.x * axis.y * cos_value) + (axis.z * sin_theta);
+        res.m[0][2] = (axis.x * axis.z * cos_value) - (axis.y * sin_theta);
+        res.m[1][0] = (axis.y * axis.x * cos_value) - (axis.z * sin_theta);
+        res.m[1][1] = (axis.y * axis.y * cos_value) + cos_theta;
+        res.m[1][2] = (axis.y * axis.z * cos_value) + (axis.x * sin_theta);
+        res.m[2][0] = (axis.z * axis.x * cos_value) + (axis.y * sin_theta);
+        res.m[2][1] = (axis.z * axis.y * cos_value) - (axis.x * sin_theta);
+        res.m[2][2] = (axis.z * axis.z * cos_value) + cos_theta;
+
+        return res;
+    }
+
+    pub fn translate(translation: Vec3) Mat4 {
+        var res = Mat4.identity();
+        res.m[3][0] = translation.x;
+        res.m[3][1] = translation.y;
+        res.m[3][2] = translation.z;
+        return res;
+    }
+};
+
+test "Vec3.zero" {
+    const v = Vec3.zero();
+    assert(v.x == 0.0 and v.y == 0.0 and v.z == 0.0);
+}
+
+test "Vec3.new" {
+    const v = Vec3.new(1.0, 2.0, 3.0);
+    assert(v.x == 1.0 and v.y == 2.0 and v.z == 3.0);
+}
+
+test "Mat4.ident" {
+    const m = Mat4.identity();
+    for (m.m, 0..) |row, y| {
+        for (row, 0..) |val, x| {
+            if (x == y) {
+                assert(val == 1.0);
+            } else {
+                assert(val == 0.0);
+            }
+        }
+    }
+}
+
+test "Mat4.mul" {
+    const l = Mat4.identity();
+    const r = Mat4.identity();
+    const m = Mat4.mul(l, r);
+    for (m.m, 0..) |row, y| {
+        for (row, 0..) |val, x| {
+            if (x == y) {
+                assert(val == 1.0);
+            } else {
+                assert(val == 0.0);
+            }
+        }
+    }
+}
+
+fn eq(val: f32, cmp: f32) bool {
+    const delta: f32 = 0.00001;
+    return (val > (cmp - delta)) and (val < (cmp + delta));
+}
+
+test "Mat4.persp" {
+    const m = Mat4.persp(60.0, 1.33333337, 0.01, 10.0);
+
+    assert(eq(m.m[0][0], 1.73205));
+    assert(eq(m.m[0][1], 0.0));
+    assert(eq(m.m[0][2], 0.0));
+    assert(eq(m.m[0][3], 0.0));
+
+    assert(eq(m.m[1][0], 0.0));
+    assert(eq(m.m[1][1], 2.30940));
+    assert(eq(m.m[1][2], 0.0));
+    assert(eq(m.m[1][3], 0.0));
+
+    assert(eq(m.m[2][0], 0.0));
+    assert(eq(m.m[2][1], 0.0));
+    assert(eq(m.m[2][2], -1.00200));
+    assert(eq(m.m[2][3], -1.0));
+
+    assert(eq(m.m[3][0], 0.0));
+    assert(eq(m.m[3][1], 0.0));
+    assert(eq(m.m[3][2], -0.02002));
+    assert(eq(m.m[3][3], 0.0));
+}
+
+test "Mat4.lookat" {
+    const m = Mat4.lookat(.{ .x = 0.0, .y = 1.5, .z = 6.0 }, Vec3.zero(), Vec3.up());
+
+    assert(eq(m.m[0][0], 1.0));
+    assert(eq(m.m[0][1], 0.0));
+    assert(eq(m.m[0][2], 0.0));
+    assert(eq(m.m[0][3], 0.0));
+
+    assert(eq(m.m[1][0], 0.0));
+    assert(eq(m.m[1][1], 0.97014));
+    assert(eq(m.m[1][2], 0.24253));
+    assert(eq(m.m[1][3], 0.0));
+
+    assert(eq(m.m[2][0], 0.0));
+    assert(eq(m.m[2][1], -0.24253));
+    assert(eq(m.m[2][2], 0.97014));
+    assert(eq(m.m[2][3], 0.0));
+
+    assert(eq(m.m[3][0], 0.0));
+    assert(eq(m.m[3][1], 0.0));
+    assert(eq(m.m[3][2], -6.18465));
+    assert(eq(m.m[3][3], 1.0));
+}
+
+test "Mat4.rotate" {
+    const m = Mat4.rotate(2.0, .{ .x = 0.0, .y = 1.0, .z = 0.0 });
+
+    assert(eq(m.m[0][0], 0.99939));
+    assert(eq(m.m[0][1], 0.0));
+    assert(eq(m.m[0][2], -0.03489));
+    assert(eq(m.m[0][3], 0.0));
+
+    assert(eq(m.m[1][0], 0.0));
+    assert(eq(m.m[1][1], 1.0));
+    assert(eq(m.m[1][2], 0.0));
+    assert(eq(m.m[1][3], 0.0));
+
+    assert(eq(m.m[2][0], 0.03489));
+    assert(eq(m.m[2][1], 0.0));
+    assert(eq(m.m[2][2], 0.99939));
+    assert(eq(m.m[2][3], 0.0));
+
+    assert(eq(m.m[3][0], 0.0));
+    assert(eq(m.m[3][1], 0.0));
+    assert(eq(m.m[3][2], 0.0));
+    assert(eq(m.m[3][3], 1.0));
+}
diff --git a/src/shaders/main.glsl b/src/shaders/main.glsl
new file mode 100644
index 0000000..48de990
--- /dev/null
+++ b/src/shaders/main.glsl
@@ -0,0 +1,33 @@
+//------------------------------------------------------------------------------
+//  shaders for offscreen-sapp sample
+//------------------------------------------------------------------------------
+@header const m = @import("../math.zig")
+@ctype mat4 m.Mat4
+
+// shared code for all shaders
+@block uniforms
+layout(binding=0) uniform vs_params {
+    mat4 mvp;
+};
+@end
+
+// offscreen rendering shaders
+@vs vs_offscreen
+@include_block uniforms
+
+in vec2 position;
+
+void main() {
+    gl_Position = vec4(position, 0, 1);
+}
+@end
+
+@fs fs_offscreen
+out vec4 frag_color;
+
+void main() {
+    frag_color = vec4(1.0, 0.5, 1.0, 1.0);
+}
+@end
+
+@program offscreen vs_offscreen fs_offscreen