1 files changed, 107 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) };
+}