Render multiple cubes

Description

In our game we're going to render many cubes to make up a world. Most of what we've built can be reused, but we'll want to put the cubes in different positions.

We've already built a transformation that can move the model cube at the origin to an arbitrary position in the world. The position is supplied to the vertex shader via a uniform which we had given a default value.

The more common use for a uniform is for the application to pass in values to the shader each time the pipeline is invoked (i.e. when we call glDrawTriangles). In this case we want to specify a new position each time we draw a cube.

Screenshot

Commands

git clone git@github.com:atsheehan/iridium
cd iridium
git checkout 0e78981dfa2fe7106f72762adc9d3132483dac62
cargo run --release

Code Changes

`Modified shaders/cube.vertGitHub`

@@ -3,7 +3,7 @@
33  const float NEAR = 0.1;
44  const float FAR = 10000.0;
55  
6- uniform vec3 position = vec3(2.0, 3.0, 6.0);
6+ uniform vec3 position;
77  
88  out vec3 vertex_color;
99

@@ -3,7 +3,7 @@
3  const float NEAR = 0.1;
4  const float FAR = 10000.0;
5  
6- uniform vec3 position = vec3(2.0, 3.0, 6.0);
7  
8  out vec3 vertex_color;
9

@@ -3,7 +3,7 @@
3  const float NEAR = 0.1;
4  const float FAR = 10000.0;
5  
6+ uniform vec3 position;
7  
8  out vec3 vertex_color;
9

`Modified src/main.rsGitHub`

@@ -1,5 +1,7 @@
1+ mod math;
12  mod render;
23  
4+ use math::Vec3;
35  use render::Renderer;
46  use winit::{
57      event::{Event, WindowEvent},
@@ -23,7 +25,10 @@
2325                  window_id,
2426              } if window_id == renderer.window_id() => {
2527                  renderer.clear();
26-                 renderer.draw_cube();
28+                 renderer.draw_cube(&Vec3(2.0, 3.0, 6.0));
29+                 renderer.draw_cube(&Vec3(-4.0, 0.0, 6.0));
30+                 renderer.draw_cube(&Vec3(5.0, 10.0, 30.0));
31+                 renderer.draw_cube(&Vec3(20.0, -23.0, 30.0));
2732                  renderer.present();
2833              }
2934              _ => (),

@@ -1,5 +1,7 @@
 
1  mod render;
2  
 
3  use render::Renderer;
4  use winit::{
5      event::{Event, WindowEvent},
@@ -23,7 +25,10 @@
23                  window_id,
24              } if window_id == renderer.window_id() => {
25                  renderer.clear();
26-                 renderer.draw_cube();
 
 
 
27                  renderer.present();
28              }
29              _ => (),

@@ -1,5 +1,7 @@
1+ mod math;
2  mod render;
3  
4+ use math::Vec3;
5  use render::Renderer;
6  use winit::{
7      event::{Event, WindowEvent},
@@ -23,7 +25,10 @@
25                  window_id,
26              } if window_id == renderer.window_id() => {
27                  renderer.clear();
28+                 renderer.draw_cube(&Vec3(2.0, 3.0, 6.0));
29+                 renderer.draw_cube(&Vec3(-4.0, 0.0, 6.0));
30+                 renderer.draw_cube(&Vec3(5.0, 10.0, 30.0));
31+                 renderer.draw_cube(&Vec3(20.0, -23.0, 30.0));
32                  renderer.present();
33              }
34              _ => (),

`Added src/math.rsGitHub`

1+ pub(crate) struct Vec3(pub(crate) f32, pub(crate) f32, pub(crate) f32);

1+ pub(crate) struct Vec3(pub(crate) f32, pub(crate) f32, pub(crate) f32);

`Modified src/render.rsGitHub`

@@ -15,6 +15,8 @@
1515      window::{Window, WindowBuilder, WindowId},
1616  };
1717  
18+ use crate::math::Vec3;
19+ 
1820  const CUBE_VERTEX_SHADER_SRC: &str = include_str!("../shaders/cube.vert");
1921  const CUBE_FRAGMENT_SHADER_SRC: &str = include_str!("../shaders/cube.frag");
2022  
@@ -100,7 +102,9 @@
100102          }
101103      }
102104  
103-     pub(crate) fn draw_cube(&mut self) {
105+     pub(crate) fn draw_cube(&mut self, position: &Vec3) {
106+         self.cube_program.set_uniform_vec3("position", position);
107+ 
104108          unsafe {
105109              gl::UseProgram(self.cube_program.gl_id());
106110              gl::BindVertexArray(self.cube_vertex_array_id);
@@ -172,6 +176,16 @@
172176      fn gl_id(&self) -> GLuint {
173177          self.id.0
174178      }
179+ 
180+     fn set_uniform_vec3(&mut self, name: &str, value: &Vec3) {
181+         let Vec3(x, y, z) = *value;
182+ 
183+         let cstr_name = CString::new(name).unwrap();
184+         let location = unsafe { gl::GetUniformLocation(self.gl_id(), cstr_name.as_ptr()) };
185+         unsafe {
186+             gl::Uniform3f(location, x, y, z);
187+         }
188+     }
175189  }
176190  
177191  struct ShaderId(GLuint);

@@ -15,6 +15,8 @@
15      window::{Window, WindowBuilder, WindowId},
16  };
17  
 
 
18  const CUBE_VERTEX_SHADER_SRC: &str = include_str!("../shaders/cube.vert");
19  const CUBE_FRAGMENT_SHADER_SRC: &str = include_str!("../shaders/cube.frag");
20  
@@ -100,7 +102,9 @@
100          }
101      }
102  
103-     pub(crate) fn draw_cube(&mut self) {
 
 
104          unsafe {
105              gl::UseProgram(self.cube_program.gl_id());
106              gl::BindVertexArray(self.cube_vertex_array_id);
@@ -172,6 +176,16 @@
172      fn gl_id(&self) -> GLuint {
173          self.id.0
174      }
 
 
 
 
 
 
 
 
 
 
175  }
176  
177  struct ShaderId(GLuint);

@@ -15,6 +15,8 @@
15      window::{Window, WindowBuilder, WindowId},
16  };
17  
18+ use crate::math::Vec3;
19+ 
20  const CUBE_VERTEX_SHADER_SRC: &str = include_str!("../shaders/cube.vert");
21  const CUBE_FRAGMENT_SHADER_SRC: &str = include_str!("../shaders/cube.frag");
22  
@@ -100,7 +102,9 @@
102          }
103      }
104  
105+     pub(crate) fn draw_cube(&mut self, position: &Vec3) {
106+         self.cube_program.set_uniform_vec3("position", position);
107+ 
108          unsafe {
109              gl::UseProgram(self.cube_program.gl_id());
110              gl::BindVertexArray(self.cube_vertex_array_id);
@@ -172,6 +176,16 @@
176      fn gl_id(&self) -> GLuint {
177          self.id.0
178      }
179+ 
180+     fn set_uniform_vec3(&mut self, name: &str, value: &Vec3) {
181+         let Vec3(x, y, z) = *value;
182+ 
183+         let cstr_name = CString::new(name).unwrap();
184+         let location = unsafe { gl::GetUniformLocation(self.gl_id(), cstr_name.as_ptr()) };
185+         unsafe {
186+             gl::Uniform3f(location, x, y, z);
187+         }
188+     }
189  }
190  
191  struct ShaderId(GLuint);