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math: add perspective camera matrix

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This commit is contained in:
Olle Lukowski 2023-09-15 20:55:30 +02:00 • committed by Stephen Gutekanst
parent b6e0539c52
commit 45b23264da
1 changed files with 38 additions and 22 deletions
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60
src/math/mat.zig
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@ -303,6 +303,35 @@ pub fn Mat(
&RowVec.init(0, 0, 0, 1),
);
}
/// Constructs a perspective projection matrix; a perspective transformation matrix
/// which transforms from eye space to clip space.
///
/// The field of view angle `fovy` is the vertical angle in radians.
/// The `aspect` ratio is the ratio of the width to the height of the viewport.
/// The `near` and `far` parameters denote the depth (z coordinate) of the near and far clipping planes.
///
/// Returns a perspective projection matrix.
pub inline fn perspective(
/// The field of view angle in the y direction, in radians.
fovy: f32,
/// The aspect ratio of the viewport's width to its height.
aspect: f32,
/// The depth (z coordinate) of the near clipping plane.
near: f32,
/// The depth (z coordinate) of the far clipping plane.
far: f32,
) Matrix {
const f = 1.0 / std.math.tan(fovy / 2.0);
const zz = (near + far) / (near - far);
const zw = (2.0 * near * far) / (near - far);
return init(
&RowVec.init(f / aspect, 0, 0, 0),
&RowVec.init(0, f, 0, 0),
&RowVec.init(0, 0, zz, -1),
&RowVec.init(0, 0, zw, 0),
);
}
},
else => @compileError("Expected Mat3x3, Mat4x4 found '" ++ @typeName(Matrix) ++ "'"),
};
@ -595,28 +624,15 @@ test "Mat4x4_translation" {
try testing.expect(math.Vec3, math.vec3(2, 3, 4)).eql(m.translation());
}
// TODO(math): the tests below violate our styleguide (https://machengine.org/about/style/) we
// should write new tests loosely based on them:
test "Mat4x4_perspective" {
const fov_radians = std.math.pi / 2.0; // Field of view in radians
const aspect_ratio = 16.0 / 9.0; // Aspect ratio
const near = 0.1; // Near clipping plane
const far = 100.0; // Far clipping plane
// test "mat.ortho" {
// const ortho_mat = mat.ortho(-2, 2, -2, 3, 10, 110);
const m = math.Mat4x4.perspective(fov_radians, aspect_ratio, near, far);
// // Computed Values
// try expectEqual(ortho_mat[0][0], 0.5);
// try expectEqual(ortho_mat[1][1], 0.4);
// try expectEqual(ortho_mat[2][2], -0.01);
// try expectEqual(ortho_mat[3][0], 0);
// try expectEqual(ortho_mat[3][1], -0.2);
// try expectEqual(ortho_mat[3][2], -0.1);
const expected = math.Mat4x4.init(&math.vec4(1.0 / (aspect_ratio * std.math.tan(fov_radians / 2.0)), 0.0, 0.0, 0.0), &math.vec4(0.0, 1.0 / std.math.tan(fov_radians / 2.0), 0.0, 0.0), &math.vec4(0.0, 0.0, -(far + near) / (far - near), -1.0), &math.vec4(0.0, 0.0, -(2.0 * far * near) / (far - near), 0.0));
// // Constant values, which should not change but we still check for completeness
// const zero_value_indexes = [_]u8{
// 1, 2, 3,
// 4, 4 + 2, 4 + 3,
// 4 * 2, 4 * 2 + 1, 4 * 2 + 3,
// };
// for (zero_value_indexes) |index| {
// try expectEqual(mat.index(ortho_mat, index), 0);
// }
// try expectEqual(ortho_mat[3][3], 1);
// }
try testing.expect(math.Mat4x4, expected).eql(m);
}