OpenGL drawing utilities for neuron visualization. More...

#include <array>
#include <vector>
#include <GLFW/glfw3.h>
#include <GL/glu.h>

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Functions
void	drawSimpleSphere (const SWCNode &node, double size=0.5f)
	Draws a simple low-polygon sphere at a node's position. More...

void	drawSimpleLine (const SWCNode &a, const SWCNode &b)
	Draws a simple line between two nodes. More...

void	drawSphere (const SWCNode &node, int slices=6, int stacks=6)
	Draws a sphere with specified geometric detail. More...

void	drawCylinder (const SWCNode &a, const SWCNode &b, int segments=6)
	Draws a cylinder connecting two nodes. More...

void	drawBoundingBox (double minX, double maxX, double minY, double maxY, double minZ, double maxZ)
	Draws an axis-aligned bounding box. More...

void	setColorByType (int type)
	Sets the OpenGL color based on SWC node type. More...

void	renderSWC (const std::vector< SWCNode > &nodes)
	Renders a complete SWC neuron morphology. More...

Detailed Description

OpenGL drawing utilities for neuron visualization.

This header provides functions for rendering 3D neuron morphologies using OpenGL. It includes utilities for drawing spheres, cylinders, and other geometric primitives that make up neuron visualizations.

Author: CPPNeuronMesher Team

Date: 2025-07-27

Version: 1.0

Copyright: MIT License

Function Documentation

◆ drawBoundingBox()

void drawBoundingBox	(	double	minX,
		double	maxX,
		double	minY,
		double	maxY,
		double	minZ,
		double	maxZ
	)

Draws an axis-aligned bounding box.

Parameters

minX	Minimum x-coordinate
maxX	Maximum x-coordinate
minY	Minimum y-coordinate
maxY	Maximum y-coordinate
minZ	Minimum z-coordinate
maxZ	Maximum z-coordinate

Renders a wireframe box representing the spatial bounds of the neuron. Uses immediate mode OpenGL line drawing.

Draws an axis-aligned bounding box.

Parameters

[in]	minX	The minimum X coordinate of the bounding box
[in]	maxX	The maximum X coordinate of the bounding box
[in]	minY	The minimum Y coordinate of the bounding box
[in]	maxY	The maximum Y coordinate of the bounding box
[in]	minZ	The minimum Z coordinate of the bounding box
[in]	maxZ	The maximum Z coordinate of the bounding box

This function draws a white wireframe box representing the spatial bounds of the neuron morphology. The box is drawn using OpenGL line primitives, with each edge of the box represented by a single line segment.

The function sets the current OpenGL color to white before rendering and uses immediate mode rendering (glBegin/glEnd). The box is axis-aligned and defined by the provided min/max coordinates in each dimension.

Note: The function sets the color to white (1.0, 1.0, 1.0); Uses legacy OpenGL immediate mode rendering; The box is drawn with GL_LINES primitive type

See also: glBegin() for details on immediate mode rendering; glVertex3f() for vertex specification

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◆ drawCylinder()

void drawCylinder	(	const SWCNode &	a,
		const SWCNode &	b,
		int	segments
	)

Draws a cylinder connecting two nodes.

Parameters

a	First node (start of cylinder)
b	Second node (end of cylinder)
segments	Number of radial segments for the cylinder [default: 6]

Renders a tapered cylinder that connects two nodes, with the radius at each end determined by the nodes' radii. The cylinder is colored according to the first node's type.

Draws a cylinder connecting two nodes.

Parameters

[in]	a	The starting node of the cylinder
[in]	b	The ending node of the cylinder
[in]	segments	The number of sides around the cylinder

This function draws a tapered cylinder connecting two nodes in 3D space. The cylinder's radius at each end is determined by the radius property of the corresponding node, allowing for smooth tapering of neurites.

The function handles the necessary coordinate system transformations to orient the cylinder correctly between the two points in 3D space. It uses OpenGL's matrix stack to ensure the transformations don't affect subsequent rendering operations.

Note: The cylinder is drawn with smooth normals for proper lighting; If the nodes are coincident (distance = 0), the function returns early; The 57.2957795f constant converts radians to degrees (180/π); Uses legacy OpenGL immediate mode rendering

See also: gluCylinder() for details on the underlying GLU primitive

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◆ drawSimpleLine()

void drawSimpleLine	(	const SWCNode &	a,
		const SWCNode &	b
	)

Draws a simple line between two nodes.

Parameters

a	First node (start point)
b	Second node (end point)

Renders a line in 3D space between two nodes using immediate mode OpenGL. The line width is determined by the nodes' radii.

Draws a simple line between two nodes.

Parameters

[in]	a	The starting node of the line
[in]	b	The ending node of the line

This function renders a simple line segment between two nodes in 3D space using OpenGL's immediate mode line rendering. The line is drawn with the current OpenGL color and line width settings.

The function is typically used for wireframe representations of neuron morphologies or for debug visualization.

Note: The line is drawn with the current OpenGL color; Uses legacy OpenGL immediate mode rendering (glBegin/glEnd); For more complex line rendering (e.g., with thickness), consider using geometry shaders or other modern OpenGL techniques

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◆ drawSimpleSphere()

void drawSimpleSphere	(	const SWCNode &	node,
		double	size
	)

Draws a simple low-polygon sphere at a node's position.

Parameters

node	The SWC node containing position and radius information
size	Scale factor for the sphere radius (default: 0.5)

This function renders a sphere using immediate mode OpenGL with minimal geometric detail, making it suitable for large numbers of nodes.

Draws a simple low-polygon sphere at a node's position.

Parameters

[in]	node	The SWCNode containing the position for the sphere
[in]	size	The radius of the sphere

This function draws a simple sphere using OpenGL's GLU quadric primitives. It's optimized for speed rather than visual quality, using a low number of slices and stacks (8x8) for the sphere approximation.

The function handles the OpenGL matrix stack appropriately, pushing the current matrix before translation and popping it afterward to avoid affecting subsequent rendering operations.

Note: The sphere is drawn with the current OpenGL color; Uses legacy OpenGL immediate mode rendering

See also: drawSphere() for a higher-quality sphere rendering alternative; gluSphere() for details on the underlying GLU primitive

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◆ drawSphere()

void drawSphere	(	const SWCNode &	node,
		int	slices,
		int	stacks
	)

Draws a sphere with specified geometric detail.

Parameters

node	The SWC node to draw
slices	Number of subdivisions around the z-axis (longitude) [default: 6]
stacks	Number of subdivisions along the z-axis (latitude) [default: 6]

Uses GLU quadric objects to render a sphere with the specified level of detail. The sphere is colored according to the node's type.

Draws a sphere with specified geometric detail.

Parameters

[in]	node	The SWCNode containing the position and radius for the sphere
[in]	slices	The number of subdivisions around the Z axis (longitude)
[in]	stacks	The number of subdivisions along the Z axis (latitude)

This function draws a sphere using OpenGL's GLU quadric primitives with smooth normal vectors for proper lighting calculations. The sphere's radius is taken from the node's radius property, and its position is set to the node's coordinates.

The function handles the OpenGL matrix stack appropriately and uses the current OpenGL color for rendering. The resolution of the sphere can be controlled through the slices and stacks parameters.

Note: The sphere is drawn with smooth shading (GLU_SMOOTH); Uses legacy OpenGL immediate mode rendering; For high-quality rendering, use at least 16 slices and stacks

See also: drawSimpleSphere() for a faster, lower-quality alternative; gluQuadricNormals() for details on normal generation

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◆ renderSWC()

void renderSWC ( const std::vector< SWCNode > & nodes )

Renders a complete SWC neuron morphology.

Parameters

nodes Vector of SWC nodes to render

This is the main rendering function that draws an entire neuron morphology. It handles the display of all nodes and connections between them, with appropriate coloring based on node types. The function respects the current rendering mode and visualization settings from globals.h.

Renders a complete SWC neuron morphology.

Parameters

[in] nodes A vector of SWCNode objects representing the neuron morphology

This function renders a complete neuron morphology from SWC node data using different rendering modes controlled by the global renderMode variable. The function handles both the rendering of nodes (soma, branch points, etc.) and the connections between them (dendrites, axons).

Supported render modes:

Mode 1: White wireframe lines between nodes
Mode 2: Colored spheres at nodes with white wireframe connections
Mode 3: Yellow simple spheres at node positions
Mode 4: Purple detailed spheres at node positions
Mode 5: Colored tapered cylinders between nodes (no spheres)
Mode 6: Colored detailed spheres with colored tapered cylinders

The function first renders all nodes according to the current render mode, then renders the connections between nodes. Node colors are determined by their SWC type using the setColorByType() function.

Note: The function uses the global renderMode variable to determine rendering style; Parent-child relationships are determined by the node.pid field; The function skips rendering of invalid parent references (pid = -1)

See also: setColorByType() for information about color mapping; drawSphere(), drawCylinder() for the actual rendering primitives

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◆ setColorByType()

void setColorByType ( int type )

Sets the OpenGL color based on SWC node type.

Parameters

type	SWC node type identifier (1-7)

Maps standard SWC node types to distinct colors for visualization. The color mapping follows the standard SWC color scheme:

1 (Soma): Red
2 (Axon): Blue
3 (Dendrite): Yellow
4 (Apical dendrite): Purple
5-7: Other standard SWC types

Parameters

[in] type The SWC node type identifier

This function maps standard SWC node types to specific colors for visualization. The color mapping is as follows:

Type 1: Red (soma)
Type 2: Green (axon)
Type 3: Blue (basal dendrite)
Type 4: Yellow (apical dendrite)
Type 5: Magenta
Type 6: Cyan
Type 7: Orange
Default: White (for any other type)

The function uses a static map for efficient type-to-color lookup and modifies the current OpenGL color state.

Note: The function modifies the OpenGL current color state; The color map is static and shared across all instances; For custom color schemes, modify the colorMap variable

See also: http://www.neuronland.org/NLMorphologyConverter/MorphologyFormats/SWC/Spec.html for SWC format specification

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Functions

Detailed Description

Function Documentation

◆ drawBoundingBox()

◆ drawCylinder()

◆ drawSimpleLine()

◆ drawSimpleSphere()

◆ drawSphere()

◆ renderSWC()

◆ setColorByType()