When you are modding TPT++ and come to writing the update routine, there are a few functions you will need to use. A reference of those is shown below.

sim->clear_area(int x, int y, int w, int h);

What it does: Clears a rectangle with specified height and width.

int x - Top left corner's x coordinate (from left towards the right)

int y - Top left corner's y coordinate (from top downwards!)

int w - The width of the rectangle

int h - The height of the rectangle

sim->create_part(int p, int x, int y, int t);

What it does: Creates a particle at a given coordinate.

int p - How the particle is created. -1 means from the code (will only create a particle if the space is empty). This is the normal way to create a particle, -2 is from the brush (don't use this), -3 means it will ignore any particles in the space and draw it anyway, and any positive number will overrite the particle at that index with this newly created particle.

int x - Particle's x coordinate

int y - Particle's y coordinate

int t - Particle's type. Use a pre-defined value, such as PT_INST.

sim->CreateBox(int x1, int y1, int x2, int y2, int t, int flags)

What it does: Utility function, creates a rectangle of a given particle.

For some reason, this uses a different way to specify a rectangle than the deleting equivalent.

int x1 - Top left corner's x coordinate

int y1 - Top right corner's y coordinate

int x2 - Bottom left corner's x coordinate (note: not the box's width!)

int y2 - Bottom left corner's y coordinate (see note above)

int t - Particle's type. Use a pre-defined value, such as PT_INST.

int flags - Un-useful value, leave it as 0

sim->CreateLine(int x1, int y1, int x2, int y2, int rx, int ry, int c, int flags)

What it does: Draws a line of a specified element from two points. (The equivalent of Shift+drag)

int x1 - Line start's x coordinate.

int y1 - Line start's y coordinate.

int x2 - Line end's x coordinate.

int y2 - Line end's y coordinate.

int rx - The line's X radius

int ry - The line's Y radius

Note: The function creates a Brush which is actually an oval with the specified X and Y radiuses.

That's why those are needed.

For a single pixel wide line, use 1 for both of the values.

int t - Particle's type. Use a pre-defined value, such as PT_INST.

int flags - Un-useful value, leave it as 0

sim->delete_part(int x, int y, int flags);

What it does: Deletes a particle (removes all the values associated it!)

int x - Particle's x coordinate

int y - Particle's y coordinate

int flags - Un-useful value, leave it as 0

sim->FloodParts(int x, int y, int t, int cm, int bm, int flags);

What it does: Starts a flood-fill from a point. (like ctrl+shift+clicking in TPT)

int x - Particle's x coordinate

int y - Particle's y coordinate

int t - Particle's type. Use a pre-defined value, such as PT_INST.

int cm - used by recursion in the code, leave it as -1

int bm - used by recursion in the code, leave it as -1

int flags - Un-useful value, leave it as 0

sim->flood_prop(int x, int y, size_t propoffset, void * propvalue, StructProperty::PropertyType proptype);

What it does: Sets a property via flood-fill. (Like PROP)

int x - Particle's x coordinate

int y - Particle's y coordinate

size_t propoffset - This is a value returned by the function offsetof(Particle, <property>).

Replace <property> with what you want, for example tmp or ctype.

void * propvalue - A reference to your property's value. One needs to define the value beforehand.

For example, when you've defined int temperature = 200;, then you should use &temperature.

StructProperty::PropertyType proptype - What kind of type the value you provided is.

For example, if you had a temperature number (as an integer), then you could use 'StructProperty::Integer'.

The types are: 'StructProperty::Integer', 'StructProperty::Float' and 'StructProperty::Uinteger'

sim->kill_part(int i) - Deletes particle 'with index 'i.(Does not use x,y location like delete_part)

What it does: Deletes a particle without the given x and y, using its index instead.

int i - The particle's index. Passed into the function as 'i'.

sim->nearest_part(int i,int t, int max_d);

What it does: Finds the nearest particle of a certain type.

int i - The particle's index. Passed into the function as 'i'.

int t - Particle's type. Use a pre-defined value, such as PT_INST.

int max_d - The maximum distance to look from. Set as -1 if you want it to be unlimited.

Returns: -1 if not found; particle index if found.

sim->parts_avg(int i, int ni, int t);

What it does: Checks if an element of type t is inbetween the two particles specified as indexes.

int i - The (first) particle's index. Passed into the function as 'i'.

int ni - The other particle's index.

int t - Particle's type. Use a pre-defined value, such as PT_INST.

It will actually only check the location directly in the middle

Returns: 0 if there isn't an element of type t in between the two, 1 if there is.

sim->part_change_type(int i, int x, int y, int t); - Changes type of particle i. t is new type, x is the x location of the particle, y is the y location of the particle.