make dot change position

[TheNewGuy]

i wanted to make the dot go from that position to the next. sort of like walking into a shop.

i tried this, but it would just show the dot at the position (100, 100)

how would i make the dot move to that position?

Code: Select all

if( x == 0 && y == 0 )
{
    apply_surface( x + 100, y + 100, dot, screen );
}

[Spikey]

Something like this?

Code: Select all

// Earlier in program, declare variables
int x = 0;     // Declare variables, they should start at 0 or something, not left blank.
int y = 0;  


// Later in program, Update function
if ( x == 0 && y == 0 )      // If position is 0,0 then set position to 100,100
{
     x = 100;
     y = 100;
}

if ( x == 100 && y == 100 )  // If position is 100,100 then set position to 0,0
{
     x = 0;
     y = 0;
}

// Render surface
apply_surface( x, y , dot, screen );

This might be better, handle key inputs and update dot position based on what keys are pressed.

Code: Select all

//Somewhere earlier on
int x = 0;     // Declare variables, they should start at 0 or something, not left blank.
int y = 0;  


// Handle Input (Pseudo code)
GetInput();                                 // Get input

if ( PlayerPressesUp == true )       // Decide how input effects dot position 
{
     y = y + 100;
}

if ( PlayerPressesDown == true )
{
     y = y - 100;
}


// Render surface
apply_surface( x, y, dot, screen );

[TheNewGuy]

i get the dot to move and all, but when the dots position is 0,0 i want the dot to jump to 100, 100. and the way i had it, it would just create a new instance of the dot at position 100,100. sorry if my first post was not clear on that.

[RyanPridgeon]

Are you clearing the background every time you draw? Otherwise the new dot will just be written straight to the screen, and the old one will remain, unil it's overwritten.

[TheNewGuy]

how do I clear the screen? i tried freeing the surface of the dot but that didn't work.

[RyanPridgeon]

No. Freeing the surface would delete the image data for the dot. That would not solve anything.

To clear the screen, you can either apply a background image, or draw a large black rectangle (using SDL_FillRect())

I also suggest you learn more of the C++ language and practise more programming before you attempt any more SDL... I don't mean to be offensive. Sorry if I am. But I made your mistake and it wasted a good month or so. Learn the language first.

[thejahooli]

No. Freeing the surface would delete the image data for the dot. That would not solve anything.

To clear the screen, you can either apply a background image, or draw a large black rectangle (using SDL_FillRect())

I also suggest you learn more of the C++ language and practise more programming before you attempt any more SDL... I don't mean to be offensive. Sorry if I am. But I made your mistake and it wasted a good month or so. Learn the language first.

exactly the same with me,watch the first minute and a half or so of gyro vorbis' getting started part 2 video ( http://www.youtube.com/watch?v=OaxckMNq0eU ) to see what you should already know.

[Ewan]

Maybe I don't quite understand your problem, but why are you drawing it at x+100 and y+100? Don't you want to MOVE the dot to 100,100, not just draw it there?

If you want to make it move, you just do this:

Code: Select all

if( x == 0 && y == 0 )
{
    x = 100;
    y = 100;
}

and presumably you have

Code: Select all

apply_surface( x, y, dot, screen );

in your game loop, so it will automatically be drawn wherever it is.