3.
Work with the Viewing tools Before
proceeding it is a good time to become familiar with navigating
around the Viewer pane. The viewer pane is set up as a perspective
view by default. You can navigate in this pane using the View
tool. The View tool can be quickly accessed using the Spacebar
to temporarily invoke viewing orthe Esc
key which removes you from your current operation . Here are some
examples using the Spacebar
hotkey:
Spacebar
- LMB to Tumble
the view.
Spacebar - MMB to Dolly
In and Out of the scene
Spacebar - RMB to Pan
the view
Spacebar
- Alt - MMB to Zoom In
and Out of the scene
Spacebar - Ctl - MMB to the right
to Zoom In
Spacebar - Ctl - MMB to the left to
Zoom Out
Spacebar - Ctl - LMB to Rotate
the view
Spacebar
- h to Home the view. |
Spend some time
getting used to tumbling and adjusting the view. As you work through
the lessons, be sure to use these view controls to help set up the
right view for your work. Later you will learn how to change the
view to an orthographic view.
4.
Go to the Geometry Level
With the geometry
object selected press i
to go into the object. Objects act as containers for geometry and
going inside provides you with a whole new working context. The
geometry level is where you will define the shape of your object
using surface operators known as SOPS.
You will notice
that although the geometry has not changed, your pane has turned
a different colour to indicate that you have entered Modeling mode.
In the Type menu, you can see the word SOP which indicates that
you are working with geometry.
5.
Clear the Object
RMB-click
on the default cube (but not the red handle) and select Delete
from the pop-up menu. This empties your object so that you can add
new surface operators. You can RMB-click
on any object to get a context sensitive menu that provides you
with some options.
Note:
If you RMB-click on the red handle then you will get a totally different
pop-up menu that offers a different set of options. Houdini's context
sensitive nature will seem to slow down you down initially but very
soon you will find yourself more productive because important options
are always at your fingertips.
You can also
clear the object by selecting Operator
> Clear Current Object (New) from the Viewer
pane menu.
6.
Create a Tube Operator
Press the tab
key again. You now have a new set of tools that work at the Houdini's
geometry (SOP) level. You can now go to Generators
and choose tube
or start typing the word tube
until Houdini recognizes it as the operation you desire.
7.
Change the Primitive Type
At the top of
the Viewer pane is the Operation Controls bar where you can change
the Primitive Type
to NURBS. This
area contains commonly used attributes for the active operator.
You could also make this change using the Parameter pane.
8.
Edit the Tube's shape
The tube appears
in the Viewer pane with a set of red handles. Most operators have
handles which allow for interactive editing of key parameters. The
handles as described below can be used to reshape the tube.
Now go to the
Parameter pane. Some of these parameters match the handles displayed
in the Viewer pane while others are unique to the Parameter pane.
Parameters can be numbers, expressions, or options chosen from a
menu.
You can change
the radius and height values using the Parameter pane. Either enter
the values directly or click drag on any field with your MMB
to call up a Value grid. The grid lets you drag left or right to
adjust the parameter value. The increments of the value change are
determined by the particular square you start dragging from.
Set the values
using either the handles or the Parameter pane so that your tube
has a height
of 2 and a
top radius of 0.45
and a bottom radius
of 0.35.
9.
Add the Nose Cone
To add a cone
to the tip of the fuselage and an exhaust to its base, you will
use a cap operator that contains several attributes suitable for
shaping the ends of the tube.
In the Viewer
pane, press tab >
Cap. The blue help text along the top of the
Houdini window prompts you to select some geometry. Since the tube
is already selected, RMB-click to
confirm the selection. This puts a flat cap on the top and bottom
of the tube.
In the parameter
pane and set the top cap
values as follows:
First
U Cap
to End Cap Rounded;
Divisions
to 5;
Scale to 2.5,
Note:
If youe MMB-drag in
the Scale
edit field, you can watch the nose of the rocket grow interactively
in the viewer pane.
10.
Add the Exhaust
In the parameter
pane, set the bottom cap
values to create the exhaust area. A negative value reverses the
shape of the cap.
Last
U Cap
to End Cap Rounded;
Scale to -0.5.
11.
Go back and edit the Tube
Tumble in shaded
mode to view the final surface. Notice how the cap isoparm lines
do not transition smoothly. This is because of the geometry settings
found in the tube operator. Since the look of the final fuselage
geometry is the result of the tube operator and the cap operator
working in sequence it is possible to go back and edit the tube
to affect the final result.
In the network
pane, click on the tube operator. In the Parameter pane, click on
the Detail tab and set the following:
Rows
to 4;
V Order to
4.
The V order
of the original tube used a degree that was best suited for straight
edges. Once the cap was added, a higher order was needed with more
detail.
12.
Save your work
From the File
menu select Save As...
Name your file and click save it in your home directory.
Part
Two: Modeling the Rocket Fins
To add detail
to the Rocket, you will create fins around the perimeter of the
fuselage. Rather than creating new objects, this new geometry will
be built within the same geometry network then merged with the fuselage
to create the final Rocket.
1.
Go to a Right View
Move your cursor
over the Viewer pane and press spacebar
- t to display four views including the perspective
view and three orthographic views. Move your cursor over the right
view and again press spacebar -
t.
Choose Wireframe
from the Shading mode menu found at the bottom of the Viewer pane.
If you don’t see this menu, click on the thin stowbar to reveal
the View controls. You
can also press w
to change to wireframe mode.
2.
Draw a Curve
With the cursor
in the Viewer pane, press tab >
Curve. The cursor changes to a small crosshair,
and the blue text at the bottom of the Houdini window prompts you
to, ‘Left-click to add points, then right-click to
complete.’
LMB-click
four times, to draw the curve. RMB-click
once to complete the drawing.
Along the top of the Viewport, make sure the Primitive
Type is set to Polygon,
the Method is
set to CVs,
and the Closed option
is checked. These parameters could also be set in the Parameter
pane and could have been chosen before drawing the curve.
3.
Extruding the Curve
Press
spacebar-t once to go to a four view layout
then move over the Perspective view and press spacebar-t
again to expand this view. With the mouse in
the Viewer pane, press tab >
Extrude. Since the curve is already selected,
RMB-click to
accept. Next RMB-click
again when prompted for a cross section. The shape is extruded by
a value of 1. You don’t need the extrusion to be so deep.
Click in the
viewport with your middle mouse button to call up a default Value
Grid. Move to one of the unit grids and click-drag
to change the value to 0.05.
This will take one edit using the 0.1 grid square and then another
in the 0.01 grid square. The value grid has been assigned to the
Depth value
of the extrusion and lets you change its value without clicking
on the attribute in the Parameter pane.
4.
Move the Fin
Press spacebar-t
to see a four view layout. In the top view, use spacebar
and your viewport controls to pan and zoom into
the views to focus your view on the fin.
With the mouse
in the Viewer pane, press tab >
Transform. Click on the Select
Whole Geometry button in the selector controls
bar then click on the fin to select all of its parts. RMB-click
to accept. A transformation handle appears to allow you to transform
your object. Click in on the X axis handle to constrain along this
direction and use the top view to help you centre the fin on the
Z axis line. In the end make sure that the X
translate value is set to -0.025
in the Parameter pane.
5.
Set Display and Template Flags
In the Network
pane, zoom in to see the cap1 tile and the new xform
tile. The display of these operators in the Viewer pane is governed
by the flag settings on each tile. For instance the xform1
operator has its Display
flag set which makes it visible and selectable. This operator's
handles are also visible in the Viewer pane. The
cap1 operator has its Footprint
flag set which also makes it visible and selectable.
Press u
to go up to the Object level. You will see only the fins. This is
because only the operator with the Display flag set is promoted
to the object level. Later you will merge the different parts of
the rocket so that everything is promoted.
Press i
to go back in. On the cap1 operator tile, click on the footprint
flag to turn it off then on the template flag to turn it on. Now
this geometry is visible in wireframe but is not selectable.
Note: You can
only have one operator's Display
flag set within a single object while you can shift-click on footprint
and template flags belonging to any number of operators.
6.
Taper the Fin
Press
tab > Transform. Press 1 to change your selection
type to points and in a right view, select all the points on the
left edge of the fin. RMB-click
to accept. This brings up a transformation handle. Press e
to display the scale handle then in a top view
click-drag on the X axis line (not the arrow) to drag along that
axis alone. Scale the points out until the fin is larger where it
touches the rocket.
7.
Create More Fins
In the Viewer
pane, press tab > Copy.
Notice the text at the bottom of your workspace informs you that
the Copy Operation wants you to select the geometry to copy –
the fin is still selected (i.e. yellow), therefore RMB-click
to accept. You are then asked if you want a template, so
RMB-click a second time to say No.
The fin is shown
with handles for positioning the copies and the Number of Copies
is set to 1. Before making new copies, you will set up an expression
to link the number of copies to the rotation of the fin around the
fuselage. In the Parameter pane, go to the Rotation-Y parameter
and type in the Expression: 360/$NCY
This expression
uses the variable $NCY (number of copies) as part of an expression
that drives the rotation around the Y axis. This makes it possible
to interactively change the number of copies and the resulting rotation
angles will be evenly spaced. You therefore have the flexibility
to change this value later.
Now use the
slider to change the Number of Copies parameter. Watch what happens
to the number of fins and how they space themselves around the base
perimeter. Because of the expression entered in the Rotation field,
Houdini spaces these copies out equally as you change the number
of copies. When you finish, set the
Number of Copies to 6.
8.
Move the Spaceship to Ground level
Click on the
footprint flag Press tab > Transform.
Press a to select
everything. The fins and the footprinted rocket are selected. RMB-click
to accept. Click-drag on the transform handle to lift the rocket
until the base of the fins sits on the ground plane.
In the Network
pane, you will see that a merge SOP has been added
before the xform SOP. Now all the geometry can be
displayed together and promoted to the Object level. Press u
to go up and see the whole rocket at the object level.
9.
Go back and Bevel the Fins
Upon review
the Rocket fins are too hard edged and require softening at the
edges. To do this you will go back up the object's history and add
new operators into the procedural network of the rocket. This ability
to insert new steps into a network's procedural history is an important
part of working with Houdini.
In the Network
pane, check the Display flag on the second xform
SOP that proceeds the copy SOP. To bevel this you
will need to fuse the corner points of the extrusion then apply
the bevel. Press tab > fuse.
Press 1 to change
your selection to points then press a to select all the points.
RMB-click
to accept. This adds a fuse operator inbetween the
xform SOP and the copy SOP.
Press tab
> PolyBevel. Press 2
to change your selection to edges then click-drag a bounding box
around all the edges except those closest to the rocket body. RMB-click
to accept. In the Parameter pane, select Absolute
then set the Absolute Inset
to 0.015. This
provides a bit of an edge to the fin that will work well when the
rocket is rendered later.
10.
Go to Object Level
When you are
finished, set the Display
flag for the last xform SOP in the chain then press
u to go back up to the Object level. Now all of your three panes
are focused on objects and the Rocket is shown sitting at the origin.
In the Network pane, click on the geo1 object name
and change it to rocket.
Part
Three: Creating a Moonscape
The rocket was
built using a series of procedures that were merged into a final
piece of geometry. To create a moonscape, you will begin manipulating
points on a surface then sculpt the same surface using a paint-based
interface.
1.
Create a New Geometry Object
In the Viewer
pane, press
tab > Geometry
then RMB-click
to accept the new object without parenting it to another object.
The new object is placed in the scene as another default cube. Rename
it moonscape.
With the moonscape
object selected in the Network pane, press i
to go down into this object's geometry level. Select and delete
the file1 operator so that you can begin building
the surface of the moon.
Make sure the
See one/all objects
button is turned off to make sure the Rocket is hidden. This button
makes it possible to work with other objects visible or hidden depending
on how you want to work. For now, you don’t need to see the
rocket to create the moonscape. Later you can turn it back on to
preview the whole scene.
2.
Create a Plane
In the Viewer
pane press, tab > Grid.
This places a new grid surface in your scene. Tumble in the Perspective
view to see the grid from an angle. In the Parameter pane, set the
following:
Size
to 5, 5;
Rows to 30;
Columns to
30.
3.
Edit Points on a Surface
Click on the
stowbar at the right edge of the Viewport to bring up the Display
options. Click on the points
button to make sure that the surface points are visible as you work.
In the Viewer pane press tab >
Edit. On the left side of the Viewport make
sure the Selector and Manipulator controls are visible and click
on the points
button. By default they will all be highlighted. It is important
to note that the Selector stowbar found on the left controls what
you select while the stowbar on the right controls what you see.
Make sure that
the Select Whole Geometry
button has been turned off so that you can focus on individual points
then click away from the grid to deselect the points. Now pick four
or five points at various points around the perimeter of the grid.
Use the Shift
key to make multiple point selections.
RMB-click to start editing. If
all points are selected with one click then you have not yet turned
off the Select Whole Geometry
button.
Click-drag up
on the vertical transform handle to drag the points along the Y
axis. This moves the points up to create small peaks. The results
appear a bit harsh and could use some softening.
4.
Soften the Edited Points
Click drag with
your MMB to
adjust the Soft Radius
of the Edit’s selection. This creates a drop off for the resulting
move. You could also adjust the Soft Radius slider at the top of
the Viewer pane to achieve the same results.
5.
Sculpt the Surface
Another way
of reshaping the surface is Houdini’s Sculpt
operation which uses a paint interface to push and pull the surface
like a piece of clay. In the Viewer pane, press tab
> Sculpt. Press a
to select all the points then RMB-click
to start sculpting. You may want to turn off Point display so that
you can focus on the surface.
Your cursor
changes to show a circle with a line pointing up from its centre.
The circle shows the brush radius and the line shows the normal
vector of the sculpt action. In the Parameter pane, set the following:
FD
(LMB displacement)
to 0.1;
Next, click
on the Brush tab and set the following:
Radius
to 0.4;
Opacity to
0.25.
You can adjust
any of these settings between brush strokes as you sculpt. Click
drag up on the surface of the grid to begin sculpting. Use your
LMB to pull
the surface and MMB
to push the surface in. Leave the centre of the grid flat while
building up the outer edge. This will create a crater for the ship
to take off from.
5.
Add More Detail
To further define
the moonscape surface, you will apply a Fractal operation that will
give an overall displacement to the grid. Press tab
> Fractal then press a to select all the
geometry. RMB-click
to apply the fractal to the selected surface. The initial results
are not ideal and you will need to adjust some parameters. Change
the following in the Parameter pane:
Divisions
to 1;
Scale to 0.025.
Reducing the
divisions simplifies the surface and the scale adjusts the size
of the displacement to suit the grid. This operation adds nice detail
to the surface. Save
your work.
Part
Four: Setting Up the Objects
You have now
experienced the Houdini workflow of creating geometry at the Modelling
level (SOP). The creation of SOP networks creates models that define
the shape of the objects in your scene. You will now return to the
object level to position the objects in space. As you work with
Houdini you will often switch back and forth between these two worlds.
1.
Scale the Moonscape
Press the u
key to go up from editing the moonscape’s shape to the object
level. This hotkey is the same as going to the Type
menu, and selecting Objects.
Now you are looking at the two objects overlapping in space. Turn
off the point display.
Press tab
> Transform. Click on the moonscape then
RMB-click to
begin transforming. Press the e
key to call up the scale handles. Scale the moonscape by about 10
times in all three directions. Use your view controls (W + [, ],
or \) to zoom out from the rocket. Now the two pieces of geometry
are working together.
2.
Add a Camera Object
To view your
objects for rendering, you will need a camera. This object type
will let you look at your scene and frame the view much like a cinematographer
does in a live action movie. In the Viewer pane, press tab
> Camera. RMB-click to add the camera to
the scene.
Use the camera
handles to move the camera's eyepoint to the rim of the crater.
Select cam1
from the Camera list at the bottom of the Viewport. The rocket is
probably not visible because the camera is not pointed in the right
direction. Click on the Lock Camera
to View button at the bottom of the Viewport
next to the Camera list. This will let you use your Viewport controls
to alter the camera’s position.
Use your Viewport
controls (W + [, ], or \) to aim the camera at the rocket. This
gives you a good starting view for your camera.
Turn the Lock Camera to View
button at the bottom of the Viewport of so that your camera and
the Viewport controls work separately. Save your work.
3.
Add a Light Object |