AC3D Tutorial - Constructing
a textured car body
Creating one side
of the car
The gif image (available
at the bottom of this page) was set as a background image on each of
the 2D windows.
'Nearsnap' was switched
on. (toggle at the bottom of the AC3D window). This 'snaps' new points
to the same position as existing points. This helps line up the points
where the top and bottom polygon join.
The polygons are
drawn in the Side view.
Two separate polygons
are used because the top polygon will be used to represent the side
windows (which will tilt inwards) and a polygon must have all of its
points on the same plane for it to be valid.
Using the background
image as a guide ensures that the polygons being made remain in the
correct proportion in relation to the texture image.
At this point -
after selecting all, Object->merge has been used to put all selected
surfaces into the same object (not shown in movie).
Extruding the 2D
side to make a 3D car body
both polygons, they are moved to the edge of the rear view image and
extruded to cover it. This ensures that the front/rear views of the
car will be the correct width for the image. The control key has been
held down when the object is dragged - this ensures that it is extruded
at 90 degrees. Not holding down the control key whilst dragging may
result in a skewed shape.
After the extrusion,
vertex select-mode is set and the roof vertices are moved inwards to
give the car's side windows a slight slope, and to line up the rear
window shape with the texture image.
Using the Texture
Coordinate Editor (TCE)to position the texture on the body
The object is set
to have the same texture image that was used as the background image.
In this case, it was already loaded, so 'rover.gif' appeared in the
The texture coordinate
editor (TCE) is accessed from the Tools menu. It allows you to position
texture coordinates, sometimes know as UV's.
After the texture
is first applied, you can see that the texture image is not correctly
mapped on the whole object. To map the surfaces, one or more surfaces
is selected and then representations of these are dragged/sized/rotated
over the image in the TCE. This specifies where on the image, each vertex
will take its position on the picture.
(In Surface select-mode)
The whole shape is selected in the main AC3D window and the surfaces
appear in the TCE. These are then selected in the TCE by dragging a
rectangle over them. The TCE Remap->side function is used to 'project'
a mapping of the image over the selected surfaces. This causes a stretched
image of the car's side to appear in the TCE - this is then scaled so
that it fits over the image. Notice how (in the 3D window) the texture
is now lined up on the sides of the car.
A similar process
is then carried out on the remaining surfaces, in three groups. The
roof/windscreen/hood, the front and the rear. The surfaces are selected
in the 3D window. This is done by holding the control key and clicking
on each surface. Additionally, holding the shift key allows extra surfaces
to be added to the current selection. Note that for the car's front,
the image first appears mirrored in the 3D window i.e. the 'Land Rover'
text is reversed. The TCE's Flip->horiz is used to flip the texture
coordinates so that the text is the correct way.
movie (3.8 meg)
This is the texture
image used in this movie. Note that this is a gif file which offers less
quality than a jpeg due to the limited range of colors available.
to save this image,
right click on it and select 'save as...'.
Points to note about this
More time can be taken when
creating the car sides to form more polygons (thus allowing the sides of the
car to be adjusted and have a curve incorporated). The wheel arches are also
not very detailed - more vertices could be inserted.
When extruding, the number
of segments is set to one. Higher values would allow more of a curved shape
to be added to the top, front and rear of the car.( Extra surfaces could be
inserted to the current model by selecting those surfaces and using Surface->Divide.
Moving the new points would add more of a 'curve' the the vehicles shape.)
The two polygons that are
initially created are seperate objects and have been merged (Object->merge),then
the object vertices have been shared (by using object->optimize vertices).
This puts all the surfaces into a single object and ensures that there were
no duplicated vertices.
The bottom surfaces of the
car have not been mapped in this example. There are also other unused parts
of the texture map e.g. mirrors and wheels. Wheels can be made simply by extruding
a disk (or an Ellipse set to surface type 'Poly').