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//! Functions and types relating to shader programs.
use std::fs;
use std::path::Path;
use std::rc::Rc;
use crate::error::Result;
use crate::graphics::opengl::GLProgram;
use crate::Context;
#[doc(inline)]
pub use crate::graphics::opengl::UniformValue;
/// The default vertex shader.
///
/// The source code for this shader is available in [`src/resources/shader.vert`](https://github.com/17cupsofcoffee/tetra/blob/master/src/resources/shader.vert).
pub static DEFAULT_VERTEX_SHADER: &str = include_str!("../resources/shader.vert");
/// The default fragment shader.
///
/// The source code for this shader is available in [`src/resources/shader.vert`](https://github.com/17cupsofcoffee/tetra/blob/master/src/resources/shader.frag).
pub static DEFAULT_FRAGMENT_SHADER: &str = include_str!("../resources/shader.frag");
/// A shader program, consisting of a vertex shader and a fragment shader.
///
/// This type acts as a lightweight handle to the associated graphics hardware data,
/// and so can be cloned with little overhead.
///
/// # Vertex Shaders
///
/// Vertex shaders take in data via three attributes:
///
/// * `a_position` - A `vec2` representing the position of the vertex in world space.
/// * `a_uv` - A `vec2` representing the texture co-ordinates that are associated with the vertex.
/// * `a_color` - A `vec4` representing a color to multiply the output by.
///
/// # Fragment Shaders
///
/// Fragment shaders have a single `vec4` output called `o_color` - this should be set to the desired output color for the
/// fragment.
///
/// # Uniforms
///
/// By default, the shader is provided with two uniform variables:
///
/// * `u_projection` - A `mat4` which can be used to translate world space co-ordinates into screen space.
/// * `u_texture` - A `sampler2D` which can be used to access color data from the currently active texture.
///
/// You can also set data into your own uniform variables via the `set_uniform` method.
#[derive(Debug, Clone, PartialEq)]
pub struct Shader {
pub(crate) handle: Rc<GLProgram>,
}
impl Shader {
/// Creates a new shader program from the given files.
pub fn new<P>(ctx: &mut Context, vertex_path: P, fragment_path: P) -> Result<Shader>
where
P: AsRef<Path>,
{
Shader::from_string(
ctx,
&fs::read_to_string(vertex_path)?,
&fs::read_to_string(fragment_path)?,
)
}
/// Creates a new shader program from the given vertex shader file.
///
/// The default fragment shader will be used.
pub fn vertex<P>(ctx: &mut Context, path: P) -> Result<Shader>
where
P: AsRef<Path>,
{
Shader::from_string(ctx, &fs::read_to_string(path)?, DEFAULT_FRAGMENT_SHADER)
}
/// Creates a new shader program from the given fragment shader file.
///
/// The default vertex shader will be used.
pub fn fragment<P>(ctx: &mut Context, path: P) -> Result<Shader>
where
P: AsRef<Path>,
{
Shader::from_string(ctx, DEFAULT_VERTEX_SHADER, &fs::read_to_string(path)?)
}
/// Creates a new shader program from the given strings.
pub fn from_string(
ctx: &mut Context,
vertex_shader: &str,
fragment_shader: &str,
) -> Result<Shader> {
ctx.gl
.compile_program(vertex_shader, fragment_shader)
.map(Shader::from_handle)
}
pub(crate) fn from_handle(handle: GLProgram) -> Shader {
Shader {
handle: Rc::new(handle),
}
}
/// Sets the value of the specifed uniform parameter.
pub fn set_uniform<V>(&mut self, ctx: &mut Context, name: &str, value: V)
where
V: UniformValue,
{
ctx.gl.set_uniform(&self.handle, name, value);
}
}