General Usage: Rendering

Most of the time, we will interface with Telescope through its public C shared library, which only contains a limited number of functions. Usually, a telescope main will look like this:

Typical main of a C++ application using Telescope

#include <telescope.h>

int main()
{
    TS_Init("<window title>", 500, 500);

    while (something)
    {
        TS_VkBeginDrawPass();
        // draw sprites here using TS_VkCmdDraw* commands
        // manipulate physics using TS_Bt* commands
        TS_VkEndDrawPass(0, 0, 0, 1);
    }

    TS_Quit();
}

Let’s talk through each of the functions used here, one by one:

Initialization & Shutdown

To initialize the telescope state, we first need to call TS_Init. This function takes three arguments:

void TS_Init(const char *ttl, int wdth, int hght)

initialize the state

Parameters

• ttl – title of the window

• wdth – window width, in pixels

• hght – window height, in pixels

Afterwards, at the end of our application, we call TS_Quit to safely quit the state and deallocate all physics and render objects

void TS_Quit()

quit the state

Drawing: Render Cycle

Each frame, Telescope will go through what is called a draw pass. <explain what that is here I have no idea>.

This always begins with TS_VkBeginDrawPass, and ends with TS_VkEndDrawPass

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Of course, we don’t just want to draw a solid color. You can draw things on the screen using the TS_VkCmdDraw* functions.

void TS_VkCmdDrawRect(float r, float g, float b, float alpha, float x, float y, float width, float height)

draw a rectangle

Parameters

• r – red component of the color (in RGBA)

• g – green component of the color (in RGBA)

• b – blue component of the color (in RGBA)

• alpha – transparency component of the color (in RGBA)

• x – x-position of the upper left corner of the rectangle

• y – y-position of the upper left corner of the rectangle

• width – size along the x-dimension

• height – size along the y-dimension

void TS_VkCmdDrawSprite(const char *image_path, float r, float g, float b, float alpha, int region_x, int region_y, int region_width, int region_height, int cell_w, int cell_h, int cell_index_i, int cell_index_j, float position_x, float position_y, float scale_x, float scale_y)

draw a sprite

Parameters

• image_path – path to image on disk

• r – red component of the color (in RGBA)

• g – green component of the color (in RGBA)

• b – blue component of the color (in RGBA)

• alpha – transparency component of the color (in RGBA)

• region_x – x-coordinate of the top left corner of the subregion

• region_y – y-coordinate of the top left corner of the subregion

• region_width – size of the subregion along the x-dimension

• region_height – size of the subregion along the x-dimension

• cell_w – width of each cell of the grid

• cell_h – height of each cell of the grid

• cell_index_i – x-index of the cell

• cell_index_j – y-index of the cell

• position_x – x-coordinate of the top left corner of the sprite

• position_y – y-coordinate of the top left corner of the sprite

• scale_x – scale along the x-dimension

• scale_y – scale along the y-dimension