"It fails" .. does not define the problem and also without rest of code and variables related to SDL_RenderDrawPoints( sdlRenderer, sdlPoints1[0], nPnts) it's hard to help.But probably you don't have defined sdlPoints1 in right way.
Original tutorial code (https://www.freepascal-meets-sdl.net/chapter-5-drawing-primitives/) shows some points but maybe only 10 instead of 500? EDIT: this works for me:Code: Pascal [Select][+][-]var sdlPoints1 : array[0..499] of TSDL_Point;begin for i := 0 to 499 do begin sdlPoints1[i].x := x + i; sdlPoints1[i].y := y + i; end; SDL_RenderDrawPoints(sdlRenderer, sdlPoints1, 500);end;