feat: add indexed drawing

citro3d/examples/cube.rs

@@ -0,0 +1,246 @@
+//! This example demonstrates the most basic usage of `citro3d`: rendering a simple
+//! RGB triangle (sometimes called a "Hello triangle") to the 3DS screen.
+
+#![feature(allocator_api)]
+
+use citro3d::macros::include_shader;
+use citro3d::math::{
+    AspectRatio, ClipPlanes, CoordinateOrientation, FVec3, Matrix4, Projection, StereoDisplacement,
+};
+use citro3d::render::ClearFlags;
+use citro3d::{attrib, buffer, render, shader, texenv};
+use ctru::prelude::*;
+use ctru::services::gfx::{RawFrameBuffer, Screen, TopScreen3D};
+
+#[repr(C)]
+#[derive(Copy, Clone)]
+struct Vec3 {
+    x: f32,
+    y: f32,
+    z: f32,
+}
+
+impl Vec3 {
+    const fn new(x: f32, y: f32, z: f32) -> Self {
+        Self { x, y, z }
+    }
+}
+
+#[repr(C)]
+#[derive(Copy, Clone)]
+struct Vertex {
+    pos: Vec3,
+    color: Vec3,
+}
+
+// borrowed from https://bevyengine.org/examples/3D%20Rendering/generate-custom-mesh/
+const VERTS: &[[f32; 3]] = &[
+    // top (facing towards +y)
+    [-0.5, 0.5, -0.5], // vertex with index 0
+    [0.5, 0.5, -0.5],  // vertex with index 1
+    [0.5, 0.5, 0.5],   // etc. until 23
+    [-0.5, 0.5, 0.5],
+    // bottom   (-y)
+    [-0.5, -0.5, -0.5],
+    [0.5, -0.5, -0.5],
+    [0.5, -0.5, 0.5],
+    [-0.5, -0.5, 0.5],
+    // right    (+x)
+    [0.5, -0.5, -0.5],
+    [0.5, -0.5, 0.5],
+    [0.5, 0.5, 0.5], // This vertex is at the same position as vertex with index 2, but they'll have different UV and normal
+    [0.5, 0.5, -0.5],
+    // left     (-x)
+    [-0.5, -0.5, -0.5],
+    [-0.5, -0.5, 0.5],
+    [-0.5, 0.5, 0.5],
+    [-0.5, 0.5, -0.5],
+    // back     (+z)
+    [-0.5, -0.5, 0.5],
+    [-0.5, 0.5, 0.5],
+    [0.5, 0.5, 0.5],
+    [0.5, -0.5, 0.5],
+    // forward  (-z)
+    [-0.5, -0.5, -0.5],
+    [-0.5, 0.5, -0.5],
+    [0.5, 0.5, -0.5],
+    [0.5, -0.5, -0.5],
+];
+
+static SHADER_BYTES: &[u8] = include_shader!("assets/vshader.pica");
+const CLEAR_COLOR: u32 = 0x68_B0_D8_FF;
+
+fn main() {
+    let mut soc = Soc::new().expect("failed to get SOC");
+    drop(soc.redirect_to_3dslink(true, true));
+
+    let gfx = Gfx::new().expect("Couldn't obtain GFX controller");
+    let mut hid = Hid::new().expect("Couldn't obtain HID controller");
+    let apt = Apt::new().expect("Couldn't obtain APT controller");
+
+    let mut instance = citro3d::Instance::new().expect("failed to initialize Citro3D");
+
+    let top_screen = TopScreen3D::from(&gfx.top_screen);
+
+    let (mut top_left, mut top_right) = top_screen.split_mut();
+
+    let RawFrameBuffer { width, height, .. } = top_left.raw_framebuffer();
+    let mut top_left_target = instance
+        .render_target(width, height, top_left, None)
+        .expect("failed to create render target");
+
+    let RawFrameBuffer { width, height, .. } = top_right.raw_framebuffer();
+    let mut top_right_target = instance
+        .render_target(width, height, top_right, None)
+        .expect("failed to create render target");
+
+    let mut bottom_screen = gfx.bottom_screen.borrow_mut();
+    let RawFrameBuffer { width, height, .. } = bottom_screen.raw_framebuffer();
+
+    let mut bottom_target = instance
+        .render_target(width, height, bottom_screen, None)
+        .expect("failed to create bottom screen render target");
+
+    let shader = shader::Library::from_bytes(SHADER_BYTES).unwrap();
+    let vertex_shader = shader.get(0).unwrap();
+
+    let program = shader::Program::new(vertex_shader).unwrap();
+    instance.bind_program(&program);
+    let mut vbo_data = Vec::with_capacity_in(VERTS.len(), ctru::linear::LinearAllocator);
+    for vert in VERTS.iter().enumerate().map(|(i, v)| Vertex {
+        pos: Vec3 {
+            x: v[0],
+            y: v[1],
+            z: v[2],
+        },
+        color: {
+            // Give each vertex a slightly different color just to highlight edges/corners
+            let value = i as f32 / VERTS.len() as f32;
+            Vec3::new(1.0, 0.7 * value, 0.5)
+        },
+    }) {
+        vbo_data.push(vert);
+    }
+
+    let mut buf_info = buffer::Info::new();
+    let (attr_info, vbo_slice) = prepare_vbos(&mut buf_info, &vbo_data);
+
+    // Configure the first fragment shading substage to just pass through the vertex color
+    // See https://www.opengl.org/sdk/docs/man2/xhtml/glTexEnv.xml for more insight
+    let stage0 = texenv::Stage::new(0).unwrap();
+    instance
+        .texenv(stage0)
+        .src(texenv::Mode::BOTH, texenv::Source::PrimaryColor, None, None)
+        .func(texenv::Mode::BOTH, texenv::CombineFunc::Replace);
+
+    let projection_uniform_idx = program.get_uniform("projection").unwrap();
+    let camera_transform = Matrix4::looking_at(
+        FVec3::new(1.8, 1.8, 1.8),
+        FVec3::new(0.0, 0.0, 0.0),
+        FVec3::new(0.0, 1.0, 0.0),
+        CoordinateOrientation::RightHanded,
+    );
+    let indices: &[u8] = &[
+        0, 3, 1, 1, 3, 2, // triangles making up the top (+y) facing side.
+        4, 5, 7, 5, 6, 7, // bottom (-y)
+        8, 11, 9, 9, 11, 10, // right (+x)
+        12, 13, 15, 13, 14, 15, // left (-x)
+        16, 19, 17, 17, 19, 18, // back (+z)
+        20, 21, 23, 21, 22, 23, // forward (-z)
+    ];
+    let indices = vbo_slice.index_buffer(indices).unwrap();
+
+    while apt.main_loop() {
+        hid.scan_input();
+
+        if hid.keys_down().contains(KeyPad::START) {
+            break;
+        }
+
+        instance.render_frame_with(|instance| {
+            let mut render_to = |target: &mut render::Target, projection| {
+                target.clear(ClearFlags::ALL, CLEAR_COLOR, 0);
+
+                instance
+                    .select_render_target(target)
+                    .expect("failed to set render target");
+
+                instance.bind_vertex_uniform(projection_uniform_idx, projection * camera_transform);
+
+                instance.set_attr_info(&attr_info);
+                unsafe {
+                    instance.draw_elements(buffer::Primitive::Triangles, &buf_info, &indices);
+                }
+            };
+
+            let Projections {
+                left_eye,
+                right_eye,
+                center,
+            } = calculate_projections();
+
+            render_to(&mut top_left_target, &left_eye);
+            render_to(&mut top_right_target, &right_eye);
+            render_to(&mut bottom_target, &center);
+        });
+    }
+}
+
+fn prepare_vbos<'a>(
+    buf_info: &'a mut buffer::Info,
+    vbo_data: &'a [Vertex],
+) -> (attrib::Info, buffer::Slice<'a>) {
+    // Configure attributes for use with the vertex shader
+    let mut attr_info = attrib::Info::new();
+
+    let reg0 = attrib::Register::new(0).unwrap();
+    let reg1 = attrib::Register::new(1).unwrap();
+
+    attr_info
+        .add_loader(reg0, attrib::Format::Float, 3)
+        .unwrap();
+
+    attr_info
+        .add_loader(reg1, attrib::Format::Float, 3)
+        .unwrap();
+
+    let buf_idx = buf_info.add(vbo_data, &attr_info).unwrap();
+
+    (attr_info, buf_idx)
+}
+
+struct Projections {
+    left_eye: Matrix4,
+    right_eye: Matrix4,
+    center: Matrix4,
+}
+
+fn calculate_projections() -> Projections {
+    // TODO: it would be cool to allow playing around with these parameters on
+    // the fly with D-pad, etc.
+    let slider_val = ctru::os::current_3d_slider_state();
+    let interocular_distance = slider_val / 2.0;
+
+    let vertical_fov = 40.0_f32.to_radians();
+    let screen_depth = 2.0;
+
+    let clip_planes = ClipPlanes {
+        near: 0.01,
+        far: 100.0,
+    };
+
+    let (left, right) = StereoDisplacement::new(interocular_distance, screen_depth);
+
+    let (left_eye, right_eye) =
+        Projection::perspective(vertical_fov, AspectRatio::TopScreen, clip_planes)
+            .stereo_matrices(left, right);
+
+    let center =
+        Projection::perspective(vertical_fov, AspectRatio::BottomScreen, clip_planes).into();
+
+    Projections {
+        left_eye,
+        right_eye,
+        center,
+    }
+}

citro3d/src/buffer.rs

@@ -5,7 +5,10 @@
 
 use std::mem::MaybeUninit;
 
+use ctru::linear::LinearAllocator;
+
 use crate::attrib;
+use crate::Error;
 
 /// Vertex buffer info. This struct is used to describe the shape of the buffer
 /// data to be sent to the GPU for rendering.
@@ -46,6 +49,62 @@ impl Slice<'_> {
     pub fn info(&self) -> &Info {
         self.buf_info
     }
+
+    /// Get an index buffer for this slice using the given indices.
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if:
+    /// - any of the given indices are out of bounds.
+    /// - the given slice is too long for its length to fit in a `libc::c_int`.
+    pub fn index_buffer<I>(&self, indices: &[I]) -> Result<Vec<I, LinearAllocator>, Error>
+    where
+        I: Index + Copy + Into<libc::c_int>,
+    {
+        if libc::c_int::try_from(indices.len()).is_err() {
+            return Err(Error::InvalidSize);
+        }
+
+        for &idx in indices {
+            let idx = idx.into();
+            let len = self.len();
+            if idx >= len {
+                return Err(Error::IndexOutOfBounds { idx, len });
+            }
+        }
+
+        Ok(unsafe { self.index_buffer_unchecked(indices) })
+    }
+
+    /// Get an index buffer for this slice using the given indices without
+    /// bounds checking.
+    ///
+    /// # Safety
+    ///
+    /// If any indices are outside this buffer it can cause an invalid access by the GPU
+    /// (this crashes citra).
+    pub unsafe fn index_buffer_unchecked<I: Index + Clone>(
+        &self,
+        indices: &[I],
+    ) -> Vec<I, LinearAllocator> {
+        let mut buf = Vec::with_capacity_in(indices.len(), LinearAllocator);
+        buf.extend_from_slice(indices);
+        buf
+    }
+}
+
+/// A type that can be used as an index for indexed drawing.
+pub trait Index: crate::private::Sealed {
+    /// The data type of the index, as used by [`citro3d_sys::C3D_DrawElements`]'s `type_` parameter.
+    const TYPE: libc::c_int;
+}
+
+impl Index for u8 {
+    const TYPE: libc::c_int = citro3d_sys::C3D_UNSIGNED_BYTE as _;
+}
+
+impl Index for u16 {
+    const TYPE: libc::c_int = citro3d_sys::C3D_UNSIGNED_SHORT as _;
 }
 
 /// The geometric primitive to draw (i.e. what shapes the buffer data describes).

citro3d/src/error.rs

@@ -1,5 +1,6 @@
 //! General-purpose error and result types returned by public APIs of this crate.
 
+use core::fmt;
 use std::ffi::NulError;
 use std::num::TryFromIntError;
 use std::sync::TryLockError;
@@ -36,6 +37,13 @@
     InvalidName,
     /// The requested resource could not be found.
     NotFound,
+    /// Attempted to use an index that was out of bounds.
+    IndexOutOfBounds {
+        /// The index used.
+        idx: libc::c_int,
+        /// The length of the collection.
+        len: libc::c_int,
+    },
 }
 
 impl From<TryFromIntError> for Error {