Low-level triangle rasterizer with depth buffering and lighting. More...

#include <rasterizer.h>

Collaboration diagram for scimesh::Rasterizer:

[legend]

Public Member Functions
	Rasterizer (int w, int h)
	Construct a rasterizer for the given output size.

void	clear (float clear_depth=1.0f)
	Clear the depth and normal buffers.

float	fog_depth_from_ndc (float z_ndc) const
	Convert a depth-buffer value to a distance in world units.

void	set_blend_mode (bool enabled)
	Enable or disable alpha blending.

void	rasterize_triangle (const Vec3 &screen_v0, const Color &color0, const Vec3 &normal0, const Vec2 &uv0, const Vec3 &screen_v1, const Color &color1, const Vec3 &normal1, const Vec2 &uv1, const Vec3 &screen_v2, const Color &color2, const Vec3 &normal2, const Vec2 &uv2, bool backface_culling, bool smooth_shading, const Vec3 &light_direction, bool wireframe, const Color &wireframe_color, Image &output)
	Rasterize a single triangle into the output image.

void	rasterize_point (float screen_x, float screen_y, float depth, float radius, const Color &color, const Vec3 &normal, const Vec3 &light_direction, Image &output)
	Rasterize a single point (filled circle) into the output image.

void	rasterize_line (const Vec3 &screen_v0, const Color &color0, const Vec3 &screen_v1, const Color &color1, float width, bool lit, const Vec3 &normal, const Vec3 &light_direction, Image &output)
	Rasterize a line segment with a screen-space width.

void	apply_ssao (Image &output, float z_near, float z_far)
	Apply screen-space ambient occlusion to the output image.

Public Attributes
Image *	active_texture = nullptr
	Optional texture image for textured meshes.

Output dimensions
int	width = 0
	Output image width in pixels.

int	height = 0
	Output image height in pixels.

Depth and normal buffers
std::vector< float >	z_buffer
	Z-buffer (depth buffer), one float per pixel.

std::vector< Vec3 >	normal_buffer
	Normal buffer, one Vec3 per pixel.

Blending
bool	blend_mode = false
	Enable alpha blending for transparent triangles (default: false).

Specular lighting
Color	specular_color = Color(0.0f, 0.0f, 0.0f, 0.0f)
	Specular highlight color.

float	shininess = 0.0f
	Shininess exponent (Phong model).

Lights
std::vector< Light >	lights
	Light sources for Blinn-Phong shading.

float	ambient = 0.3f
	Ambient light level (0.0–1.0, default: 0.3).

Post-processing
float	contrast = 1.0f
	Contrast adjustment (1.0 = no change).

Fog
bool	fog_enabled = false
	Enable depth fog (default: false).

float	fog_start = 0.0f
	Distance where fog begins (default: 0).

float	fog_end = 1.0f
	Distance where fog is fully opaque (default: 1).

FogSpace	fog_space = FogSpace::WORLD
	The space (and unit) of `fog_start` / `fog_end` (default: `FogSpace::WORLD`).

float	z_near = 0.1f
	Near plane distance of the current projection (default: 0.1).

float	z_far = 10000.0f
	Far plane distance of the current projection (default: 10000.0).

bool	orthographic = false
	Whether the current projection is orthographic (default: false).

Color	fog_color = TRANSPARENT_BLACK
	The fog color (what distant objects blend into).

SSAO (Screen-Space Ambient Occlusion)
bool	ssao_enabled = false
	Enable SSAO (default: false).

float	ssao_radius = 16.0f
	SSAO sample radius in pixels (default: 16).

float	ssao_intensity = 0.8f
	SSAO darkening intensity (0.0–1.0, default: 0.8).

Detailed Description

Low-level triangle rasterizer with depth buffering and lighting.

The Rasterizer is the heart of the rendering pipeline. It takes triangles in screen space (after all transforms have been applied) and fills in the corresponding pixels, applying:

Z-buffering (depth testing): only the closest surface at each pixel is kept.
Blinn-Phong shading: per-pixel lighting with ambient, diffuse, and specular components.
Texture mapping: bilinear sampling from an optional texture image.
Fog: linear depth fog for atmospheric effects.
SSAO: screen-space ambient occlusion for crevice darkening.

Usage

You typically don't create a Rasterizer directly; it is managed internally by Renderer. However, for advanced use:

Rasterizer rast(800, 600);
rast.lights.push_back(Light{Vec3(0,0,1), Color(1,1,1), 1.0f, true});
rast.ambient = 0.4f;
rast.clear();  // clear depth and normal buffers
// ... feed triangles via rasterize_triangle() ...

See also: Renderer, Mesh, RenderOptions

Definition at line 45 of file rasterizer.h.

Constructor & Destructor Documentation

◆ Rasterizer()

scimesh::Rasterizer::Rasterizer	(	int	w,
		int	h
	)

Construct a rasterizer for the given output size.

Allocates depth and normal buffers.

Parameters

w	Output width in pixels.
h	Output height in pixels.

Definition at line 12 of file rasterizer.cpp.

Member Function Documentation

◆ apply_ssao()

void scimesh::Rasterizer::apply_ssao	(	Image &	output,
		float	z_near,
		float	z_far
	)

Apply screen-space ambient occlusion to the output image.

Uses the depth and normal buffers to darken crevices and corners. Must be called after all triangles have been rasterized.

Parameters

[in,out] output The image to modify.

Apply screen-space ambient occlusion to the output image.

Uses the depth and normal buffers filled by rasterize_triangle() to darken creases and contact areas. Requires ssao_enabled.

The depth buffer holds normalized device depth ([-1, 1], see ndc_to_screen()); the matching camera planes have to be passed here so that distances in world units can be recovered (the same inversion that world-space fog uses). Set orthographic when the scene was rendered with a parallel projection.

Parameters

[in,out]	output	The rendered image to darken.
	z_near	Near plane distance of the camera.
	z_far	Far plane distance of the camera.

See also: fog_depth_from_ndc(), ssao_enabled

Definition at line 410 of file rasterizer.cpp.

◆ clear()

void scimesh::Rasterizer::clear ( float clear_depth = 1.0f )

Clear the depth and normal buffers.

Must be called at the start of each frame.

Parameters

clear_depth Initial depth value (default: 1.0 = farthest).

Definition at line 15 of file rasterizer.cpp.

◆ fog_depth_from_ndc()

float scimesh::Rasterizer::fog_depth_from_ndc ( float z_ndc ) const

Convert a depth-buffer value to a distance in world units.

Used for world-space fog (FogSpace::WORLD): the rasterizer only has the normalized device depth of a fragment, so the corresponding distance from the camera is recovered with the inverse of the projection (perspective or orthographic, selected by orthographic):

perspective: d = (2*n*f) / (f + n - z_ndc * (f - n))
orthographic: d = (z_ndc * (f - n) + f + n) / 2

where n = z_near and f = z_far. Both formulas are exact, because the depth buffer stores z_ndc for both projection types.

Parameters

z_ndc Depth-buffer value (normalized device depth, [-1, 1]; -1 = near plane, +1 = far plane).

Returns: Distance from the camera in world units, measured along the viewing direction.

See also: FogSpace, fog_space

Definition at line 49 of file rasterizer.cpp.

◆ rasterize_line()

void scimesh::Rasterizer::rasterize_line	(	const Vec3 &	screen_v0,
		const Color &	color0,
		const Vec3 &	screen_v1,
		const Color &	color1,
		float	width,
		bool	lit,
		const Vec3 &	normal,
		const Vec3 &	light_direction,
		Image &	output
	)

Rasterize a line segment with a screen-space width.

The segment is drawn as a series of stamps along its dominant screen axis (DDA), with linearly interpolated color and depth. This is the counterpart of rasterize_point() for line layers and is used by the renderer for LineLayer geometry, which has no world-space thickness.

Depth testing, fog, contrast and alpha blending behave exactly like for triangles and points, so lines can be occluded by meshes and vice versa. Zero-length segments degenerate to a single stamp (a dot).

Parameters

	screen_v0,screen_v1	Screen-space endpoints (x, y, depth).
	color0,color1	Colors at the two endpoints.
	width	Line width in device pixels (the caller scales by the supersampling factor, exactly like the radius of rasterize_point()).
	lit	Whether to shade the line; false draws the flat color (the default for lines).
	normal	Surface normal, used only when `lit` is true.
	light_direction	Light direction, used only when `lit` is true.
[in,out]	output	The output image.

Definition at line 349 of file rasterizer.cpp.

◆ rasterize_point()

void scimesh::Rasterizer::rasterize_point	(	float	screen_x,
		float	screen_y,
		float	depth,
		float	radius,
		const Color &	color,
		const Vec3 &	normal,
		const Vec3 &	light_direction,
		Image &	output
	)

Rasterize a single point (filled circle) into the output image.

The point is drawn as a circle of the given radius (in screen pixels). Depth testing is performed at the circle center.

Parameters

	screen_x,screen_y	Screen-space center position.
	depth	Depth value for z-buffering.
	radius	Circle radius in screen pixels.
	color	Point color.
	normal	Surface normal (for lighting).
	light_direction	Light direction for shading.
[in,out]	output	The output image.

Definition at line 328 of file rasterizer.cpp.

◆ rasterize_triangle()

void scimesh::Rasterizer::rasterize_triangle	(	const Vec3 &	screen_v0,
		const Color &	color0,
		const Vec3 &	normal0,
		const Vec2 &	uv0,
		const Vec3 &	screen_v1,
		const Color &	color1,
		const Vec3 &	normal1,
		const Vec2 &	uv1,
		const Vec3 &	screen_v2,
		const Color &	color2,
		const Vec3 &	normal2,
		const Vec2 &	uv2,
		bool	backface_culling,
		bool	smooth_shading,
		const Vec3 &	light_direction,
		bool	wireframe,
		const Color &	wireframe_color,
		Image &	output
	)

Rasterize a single triangle into the output image.

The triangle vertices are in screen space (pixel coordinates with depth). This function performs:

Bounding-box culling
Barycentric interpolation of color, normal, UV, and depth
Z-buffer depth testing
Backface culling (if enabled)
Per-pixel shading (or flat shading if smooth_shading is false)
Wireframe edge drawing (if enabled)

Triangles are shaded two-sided: a fragment whose back side is visible (positive screen-space area) and whose normal points away from the camera (normal.z < 0, i.e. the normals are expected in view space) is lit with the normal flipped towards the viewer. Coincident front/back face pairs therefore shade identically, independently of which of the two wins the depth test.

Parameters

	screen_v0,screen_v1,screen_v2	Screen-space vertex positions.
	color0,color1,color2	Per-vertex colors.
	normal0,normal1,normal2	Per-vertex normals (view space).
	uv0,uv1,uv2	Per-vertex texture coordinates.
	backface_culling	Whether to cull backfaces.
	smooth_shading	Whether to interpolate normals.
	light_direction	Light direction for shading.
	wireframe	Whether to draw wireframe edges.
	wireframe_color	Color for wireframe edges.
[in,out]	output	The output image to draw into.

Definition at line 162 of file rasterizer.cpp.

◆ set_blend_mode()

void scimesh::Rasterizer::set_blend_mode ( bool enabled )

inline

Enable or disable alpha blending.

Parameters

enabled If true, transparent fragments blend with the existing pixel color.

Definition at line 218 of file rasterizer.h.

Member Data Documentation

◆ active_texture

Image* scimesh::Rasterizer::active_texture = nullptr

Optional texture image for textured meshes.

Set this before rasterizing textured triangles. The triangle's UV coordinates are used to sample this image.

See also: Image, Mesh::texture

Definition at line 331 of file rasterizer.h.

◆ ambient

float scimesh::Rasterizer::ambient = 0.3f

Ambient light level (0.0–1.0, default: 0.3).

Uniform fill light that prevents completely black shadows.

Definition at line 112 of file rasterizer.h.

◆ blend_mode

bool scimesh::Rasterizer::blend_mode = false

Enable alpha blending for transparent triangles (default: false).

When enabled, transparent fragments blend with the existing pixel color instead of overwriting it. When disabled, only fully opaque fragments are drawn (alpha is ignored after the depth test).

Definition at line 81 of file rasterizer.h.

◆ contrast

float scimesh::Rasterizer::contrast = 1.0f

Contrast adjustment (1.0 = no change).

Definition at line 120 of file rasterizer.h.

◆ fog_color

Color scimesh::Rasterizer::fog_color = TRANSPARENT_BLACK

The fog color (what distant objects blend into).

Definition at line 161 of file rasterizer.h.

◆ fog_enabled

bool scimesh::Rasterizer::fog_enabled = false

Enable depth fog (default: false).

Definition at line 128 of file rasterizer.h.

◆ fog_end

float scimesh::Rasterizer::fog_end = 1.0f

Distance where fog is fully opaque (default: 1).

Interpreted in the space given by fog_space.

Definition at line 138 of file rasterizer.h.

◆ fog_space

FogSpace scimesh::Rasterizer::fog_space = FogSpace::WORLD

The space (and unit) of fog_start / fog_end (default: FogSpace::WORLD).

If FogSpace::WORLD, the values are converted from the depth buffer using z_near, z_far and orthographic.

See also: FogSpace

Definition at line 144 of file rasterizer.h.

◆ fog_start

float scimesh::Rasterizer::fog_start = 0.0f

Distance where fog begins (default: 0).

Interpreted in the space given by fog_space.

Definition at line 133 of file rasterizer.h.

◆ height

int scimesh::Rasterizer::height = 0

Output image height in pixels.

Definition at line 53 of file rasterizer.h.

◆ lights

std::vector<Light> scimesh::Rasterizer::lights

Light sources for Blinn-Phong shading.

If empty, a default directional light from +Z is used.

See also: Light

Definition at line 107 of file rasterizer.h.

◆ normal_buffer

std::vector<Vec3> scimesh::Rasterizer::normal_buffer

Normal buffer, one Vec3 per pixel.

Stores the surface normal at each pixel for SSAO computations.

Definition at line 69 of file rasterizer.h.

◆ orthographic

bool scimesh::Rasterizer::orthographic = false

Whether the current projection is orthographic (default: false).

Affects the depth-buffer -> world-units conversion for world-space fog.

Definition at line 158 of file rasterizer.h.

◆ shininess

float scimesh::Rasterizer::shininess = 0.0f

Shininess exponent (Phong model).

Higher values = sharper highlights. Typical range: 16–128.

Definition at line 96 of file rasterizer.h.

◆ specular_color

Color scimesh::Rasterizer::specular_color = Color(0.0f, 0.0f, 0.0f, 0.0f)

Specular highlight color.

Set to a non-transparent color to enable specular highlights.

Definition at line 91 of file rasterizer.h.

◆ ssao_enabled

bool scimesh::Rasterizer::ssao_enabled = false

Enable SSAO (default: false).

Definition at line 169 of file rasterizer.h.

◆ ssao_intensity

float scimesh::Rasterizer::ssao_intensity = 0.8f

SSAO darkening intensity (0.0–1.0, default: 0.8).

Definition at line 175 of file rasterizer.h.

◆ ssao_radius

float scimesh::Rasterizer::ssao_radius = 16.0f

SSAO sample radius in pixels (default: 16).

Definition at line 172 of file rasterizer.h.

◆ width

int scimesh::Rasterizer::width = 0

Output image width in pixels.

Definition at line 50 of file rasterizer.h.

◆ z_buffer

std::vector<float> scimesh::Rasterizer::z_buffer

Z-buffer (depth buffer), one float per pixel.

Stores the depth of the closest surface at each pixel. A new triangle only overwrites a pixel if its depth is closer.

Definition at line 64 of file rasterizer.h.

◆ z_far

float scimesh::Rasterizer::z_far = 10000.0f

Far plane distance of the current projection (default: 10000.0).

Only used to convert depth-buffer values to world units for world-space fog.

Definition at line 154 of file rasterizer.h.

◆ z_near

float scimesh::Rasterizer::z_near = 0.1f

Near plane distance of the current projection (default: 0.1).

Only used to convert depth-buffer values to world units for world-space fog.

Definition at line 149 of file rasterizer.h.

The documentation for this struct was generated from the following files:

src/core/scimesh/rasterizer.h
src/core/rasterizer.cpp

Public Member Functions

Public Attributes

Detailed Description

Usage

Constructor & Destructor Documentation

◆ Rasterizer()

Member Function Documentation

◆ apply_ssao()

◆ clear()

◆ fog_depth_from_ndc()

◆ rasterize_line()

◆ rasterize_point()

◆ rasterize_triangle()

◆ set_blend_mode()

Member Data Documentation

◆ active_texture

◆ ambient

◆ blend_mode

◆ contrast

◆ fog_color

◆ fog_enabled

◆ fog_end

◆ fog_space

◆ fog_start

◆ height

◆ lights

◆ normal_buffer

◆ orthographic

◆ shininess

◆ specular_color

◆ ssao_enabled

◆ ssao_intensity

◆ ssao_radius

◆ width

◆ z_buffer

◆ z_far

◆ z_near