Encyclopaedia Index

AC3D Modeller

Contents Introduction Examples Features AC3D and PHOENICS

# 1: Introduction

AC3D is a popular 3D object/scene modeller available for Linux, Windows 95/NT, and SGI. It is very easy to use but powerful too - anyone can create good looking 3d objects in minutes.

# 2: Examples

Some models built with AC3D (VRML files)

stadium (37kW) plane(15k)

Someone's desk... (37k) Car(13k) 

Webpages are available that show off some models that AC3D users have built - some of the models are downloadable.

# 3: Features

Platforms:

• Multi platform program -

  • Windows 95/68/NT,
  • Linux, SGI,
  • Solaris,
  • HP.

• AC3D file format compatible across platforms.

User Interface:

• Easy to use intuitive interface.
• 4 views - 3 orthographic and one 3D at once or individual views.
• Named objects can be searched for within a scene.
• Navigate/Zoom around the 2d views with cursor keys and other single key presses.
• Hierarchical view window.
• Hide/unhide objects for easier/faster editing of complicated scenes.
• Built-in fast OpenGL 3D renderer with adjustable field-of-view - instantly see results of your actions in 3D. Spin the model or switch into 'walk mode' for Quake-style control.
• Headlight and up to 7 other positionable lights.
• 24-bit colour palette with adjustable diffuse; ambient; emissive; specular; shininess and transparency.
• Texture mapping support with real-time rendering.
• Configurable to use external renderers such as Povray and BMRT - just select Tools->Render to start.
• Plugin interface (registered versions only) with source code for existing plugins and a software development kit.

Modelling features:

• Adjustable 2D and 3D grid guide lines with grid-snap function
• Edit at different granularity - groups, objects, vertices
• Full polygon editing. Not just spheres, cubes etc - make a sphere and move the points (vertices) to deform the shape.
• Manipulate individual surfaces:
  • insert/remove vertices
  • make holes
  • spike
  • spline
  • bevel
  • triangulate
  • flip
  • group into new objects
• Create new surfaces/objects around any selection (Convex hull)
• Extrude and revolve 2D lines to make 3D shapes.
• Scale a selection to a specific size.
• Flip a selection (mirror) about X, Y or Z axis.
• Optimize duplicate vertices and surfaces.

File formats:

• Simple documented file formats allow easy conversion from other forms of data - ideal for visualizing your own data in 3D.
• Supports many output/input formats including:
  • 3D-studio
  • Lightwave
  • Alias triangle
  • DXF
  • VRML1 and 2 and Inventor
  • Povray
  • RIB
  • Triangles
  • Direct X (via plugin)

AC3D and PHOENICS

Purpose of AC3D for PHOENICS Users

• The creation of facetted objects representing the various elements of the flow geometry.
• Modification of exisiting geometries - change shape and/or colour.
• Repair of existing CAD geometries.

General Rules for Creation of Faceted Objects

• Object must be 3D, even if it is to be used as a 2D object in PHOENICS.
• All normals must point outwards.
• Object must be a closed volume.

CHAM Plug-ins

• Import formats -

  • CHAM .dat geometry files
  • STL files
  • DXF files

• Export formats -

  • CHAM .dat files
  • STL files

• Utilities -

  • Heal holes in object
  • Orient all faces in same direction
  • Split into component parts
  • Run Shapemaker
  • Boolean operations-
    • Subtract
    • Union
    • Intersect

Examples

The aeroplane example shown above was downloaded from the internet and loaded into AC3D:

A PHOENICS dat file was exported, and used as the geometry for an object:

Inlet and outlet boundary conditions were added, and the solution of velocities and pressure was turned on, together with the KECHEN turbulence model. The solution produced the following pictures:

Pressure on the centre-line and body surface.

Streamlines starting on circles upstream of the plane.

Closer study of the solution showed that the wings generate negative lift, because of the peculiar cross-section chosen by the anonymous creator.

Pressure on cross section of left wing

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