Advanced Computer Graphics Project 6

Project 6: Advanced Computer Graphics: C-Script Editing with SED

Reference for this project: Chapter 7 (Link to page of draft book chapter. )

Save the pieces of the project so you can later demonstrate each one
On university computers, the SED editor may freeze temporarily. To avoid this problem, disable automatic backup with MenuBar->Options->Preferences and uncheck the backup item, click OK. If SED crashes, open SED a second time and check that the preference was set. You may also need to do this each time that you log in.

Make a directory ~/video/project6 in your home directory
Comlex levels have complex script files and would be difficult to navigate. To make it easier to learn the basics of C-script and SED, we will start with an extremely simple level. Do not use your previous projects with complicated levels.
Using WED, create a simple level consisting of a single textured large plate floor as shown below, and save it as game6.wmd. It is best if the plate is centered at the origin.

Figure 1. An extremely simple level.

Basic Output: Error messages

Error messages can be helpful in debugging code and interrupting code execution.
Open the game script "game6.wdl"

Add a pop-up error message using the error() function.as described in "Adding an Error Message" section of the book.
Have the error message print out "Test 1."
Place the error ahead of the “main game loop” .
Save the script and rebuild and run the game.

The message box should appear as below, except with the message "Test 1."
Q1 Does the game stop running until OK is pressed?.

Figure 2. Error message.

Adding Actions

Actions are pretty much what the name implies, they are actions that an entity performs. And entities are models that have associated actions. For example, if you have a player in a level and it has no associated action, it will not move or do anything in the game.
To experiment with actions, add an action to rotate a model to your "game6.wdl" script, as described in the "Adding Actions to Entites" section of the book.
Call the action "tw_rotate"
Use the statement "my.pan = my.pan + angleIncrement;" to create the rotation
After adding the code for the action, save the script.
Open the level in WED, and add a player with PlBiped01 behavior, and add a camera3rd01 camera.
Add a second model such as a fish (seen below), and add to it the new behavior "tw_rotate" by rightclicking the model and adding the behavior. (The behavior appears in the menu of available behaviors after it is added to the script file.)

Figure 3. Player and fish added.

Rebuild and run the game.
The fish should spin! Try the other axes,“.pan” with “.tilt,” or “.roll”
Q2 How long does it take the fish to turn 360 degrees?

Adding Keyboard Controls and If Statements

Next, add keyboard control over the action, as described in the "If Statements and Movement of Entites" section of the book.
Use the built-in "key_f" macro/keyboard-function to test is the "f" key is pressed on the keyboard.
When the "f" key is pressed, make the fish float upward using the statement "my.z = my.z + zIncrement;"
When the key is not pressed, the fish should float downward, but stop above the floor.
Q3 If you do not prevent it, will the fish pass through the floor, or will it collide and stop?

Adding Functions and Triggers

A trigger is an action that happens when a player-entity comes close to a trigger-entity.
Next, add another fish to the level.
Add a function tw_float_away_func() that uses the statement "my.z = my.z + zIncrement;" to make the fish float away forever. Use a while(1) loop, an dont forget to add a wait(1) statement inside the loop so it doesnt crash.
Create the action tw_float_away including the statement "my.event = tw_float_away_func;"
Save the new script.
In WED add the action tw_float_away to the new fish.
Rebuild and run the game.
The fish should float away when the player touches the new fish!
Q4 If you comment out the while(1) statement in tw_float_away_func(), what happens when the player keeps bumping into the fish?
The new two-fish game should look something like:

Figure 3. Player and second fish added.

Creating and Animating New Entities

Up to this point models and player entities have been added to the game from within WED. It is also possible to create entities from within a script. This may be useful in making characters appear and disappear from a game, or for making other objects appear or disappear.
The following method creates an entity and animates it with the walk cycle.
This would be one way to test your model animation cycles in the game engine.
Use an adaptation of the following code to make your model from the previous project appear in the game:

var tw_walk_counter;
action tw_walk
{
    while(1) //start loop
    {
    tw_walk_counter = tw_walk_counter + 1;     //add to walk counter
    //ent_frame("walk",tw_walk_counter);         //old style syntax, pre 6.31
    ent_animate(me,"walk",tw_walk_counter,ANM_CYCLE+ANM_ADD); //new syntax
    if(tw_walk_counter >= 100)
    {
        tw_walk_counter = 0;                                 // reset counter at 100 percent
    }
    wait(1);
   }
}
var tw_mod_vector[3]=30,40,50;                           // where entity is located
string mod_name = <animatedmodel1.mdl>;             //file name of fish entity
function tw_create_mod1() //called by pressing "p"
{
ent_create (mod_name, tw_mod_vector, tw_walk);    //create the fish entity
}

Add a call to the function right before the main game loop (i.e. add the statement "tw_create_mod1();" right before the main loop.)
Add a function prototype after the include statements and before main()
Rebuild and run the game.
You should see the model walking on the floor!

Figure 4. Another model added from within script at corner.

Q5 What vector setting for tw_mod_vector places the model at the corner of the floor plate, as illustrated above?
Q6 What are the coordinates of the corner of the floorplate in WED?

Gravity and Collision Detection

A simple way to simulate gravity is do decrement the z coordinate.
In the previous code for action tw_walk,

change the initial vector to "tw_mod_vector[3]=0,100,100;"
and add the following two lines immediately after the ent_animate(...) line:

me.z=me.z-1;
me.x=me.x+0.5;

Rebuild and run the game.
The added character should start above the ground and disappear into the floor.
This is because there is no collision detection in the way the movement was implemented using the statement "me.z=me.z-1"
Next, add a collision-based move and name the new action tw_walk_collision and add a new function to create a second model entity and name the new entity-creation-function tw_create_mod2() ... following along the lines of the template of tw_create_mod1().
See the "Simple Gravity and Collision Detection" section of the book
Add a call to the function right before the main game loop
Add a function prototype after the include statements and before main()
Add a new "var tw_mod_vector2[3]=0,50,100;" so this new character walks along side the first one
To implement collision detection use statements along the lines of:

var tw_errresult=0;
var tw_walk_incr[3]=0.25,0,0;
var tw_walk_gravity[3]=0,0,-1;
move_mode =IGNORE_PASSABLE+GLIDE
tw_errresult=ent_move(tw_walk_incr, tw_walk_gravity); //collision detect move

After editing the script, save it.
Rebuild and rerun the game.
Demonstrate that the model no longer goes through the floor!
Hopefully, you will see one entity heading through the floor and one colliding as below:

Figure 5. Two entities in front of player with one going through floor.

Q7 What happens if the player walks off the edge?
Q8 How far into the floor does the collision-based-move entity go?
Q9 After "bottoming out" does the collision-based-move entity glide?
Change your script to use c_move() instead of ent_move() for polygon presise movement.
Q10 Does the collision-based-move entity now hit the floor and glide on its feet?

Report and demonstration:

Prepare a 12-page report exactly in the following format;

Cover sheet with names
1 Page summary of project
1 Page Printout from the running game showing the error message as in Figure 2.
1 Page Printout from WED showing model and 2 fish, as in Figure 3 above.
1 Page Printout from the running game showing the entity in the corner as in Figure 4.
1 Page Printout from the running game showing the 2 entities as in Figure 5.
5 (or more) Page Printout from SED showing game6.wdl.
1 Page Short answers to the following questions:

Q1 above
Q2 above
Q3 above
Q4 above
Q5 above
Q6 above
Q7 above
Q8 above
Q9 above
Q10 above

<>Demonstration: Show your

error message
"key-f" floating fish,
trigger-fish,
move-through-floor entity,
ent_move() entity,
c_move()-entity.

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