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alacritty
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Use indexed drawing to draw quads

This commit is contained in:
Joe Wilm 2016-02-24 20:11:15 -08:00
parent 24b4c3ba47
commit 5226666690
1 changed files with 24 additions and 15 deletions
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39
src/main.rs
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@ -54,22 +54,36 @@ fn main() {
let mut vao: GLuint = 0;
let mut vbo: GLuint = 0;
let mut ebo: GLuint = 0;
unsafe {
gl::GenVertexArrays(1, &mut vao);
gl::GenBuffers(1, &mut vbo);
gl::GenBuffers(1, &mut ebo);
gl::BindVertexArray(vao);
gl::BindBuffer(gl::ARRAY_BUFFER, vbo);
gl::BufferData(
gl::ARRAY_BUFFER,
(size_of::<f32>() * 6 * 4) as GLsizeiptr,
(size_of::<f32>() * 4 * 4) as GLsizeiptr,
ptr::null(),
gl::DYNAMIC_DRAW
);
let indices: [u32; 6] = [0, 1, 3,
1, 2, 3];
gl::BindBuffer(gl::ELEMENT_ARRAY_BUFFER, ebo);
gl::BufferData(gl::ELEMENT_ARRAY_BUFFER,
6 * size_of::<u32>() as isize,
indices.as_ptr() as *const _,
gl::STATIC_DRAW);
gl::EnableVertexAttribArray(0);
gl::VertexAttribPointer(0, 4, gl::FLOAT, gl::FALSE, 4 * size_of::<f32>() as i32,
ptr::null());
gl::BindBuffer(gl::ARRAY_BUFFER, 0);
gl::BindBuffer(gl::ELEMENT_ARRAY_BUFFER, 0);
gl::BindVertexArray(0);
}
@ -81,7 +95,7 @@ fn main() {
gl::Clear(gl::COLOR_BUFFER_BIT);
}
render(&program, &glyph_j, &tex, vbo, vao);
render(&program, &glyph_j, &tex, vbo, vao, ebo);
window.swap_buffers();
@ -100,10 +114,8 @@ fn get_rect(glyph: &RasterizedGlyph, x: f32, y: f32) -> Rect<f32> {
}
/// Render a character
///
/// TODO use element array to describe quad instead
fn render(program: &ShaderProgram, glyph: &RasterizedGlyph, tex: &AlphaTexture, vbo: GLuint,
vao: GLuint)
vao: GLuint, ebo: GLuint)
{
program.activate();
unsafe {
@ -114,14 +126,11 @@ fn render(program: &ShaderProgram, glyph: &RasterizedGlyph, tex: &AlphaTexture,
let rect = get_rect(glyph, 10.0, 10.0);
// top right of character
let vertices: [[f32; 4]; 6] = [
[rect.min_x(), rect.max_y(), 0., 0.],
[rect.min_x(), rect.min_y(), 0., 1.],
[rect.max_x(), rect.min_y(), 1., 1.],
[rect.min_x(), rect.max_y(), 0., 0.],
[rect.max_x(), rect.min_y(), 1., 1.],
let vertices: [[f32; 4]; 4] = [
[rect.max_x(), rect.max_y(), 1., 0.],
[rect.max_x(), rect.min_y(), 1., 1.],
[rect.min_x(), rect.min_y(), 0., 1.],
[rect.min_x(), rect.max_y(), 0., 0.],
];
unsafe {
@ -133,13 +142,13 @@ fn render(program: &ShaderProgram, glyph: &RasterizedGlyph, tex: &AlphaTexture,
gl::BufferSubData(
gl::ARRAY_BUFFER,
0,
(4 * 6 * size_of::<f32>()) as isize,
(4 * 4 * size_of::<f32>()) as isize,
vertices.as_ptr() as *const _
);
gl::BindBuffer(gl::ARRAY_BUFFER, 0);
gl::BindBuffer(gl::ELEMENT_ARRAY_BUFFER, ebo);
gl::DrawArrays(gl::TRIANGLES, 0, 6);
gl::DrawElements(gl::TRIANGLES, 6, gl::UNSIGNED_INT, ptr::null());
gl::BindVertexArray(0);
gl::BindTexture(gl::TEXTURE_2D, 0);
}