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Diffstat (limited to 'generator/pamtris/framebuffer.c')
| -rw-r--r-- | generator/pamtris/framebuffer.c | 339 |
1 files changed, 339 insertions, 0 deletions
diff --git a/generator/pamtris/framebuffer.c b/generator/pamtris/framebuffer.c new file mode 100644 index 00000000..93263c91 --- /dev/null +++ b/generator/pamtris/framebuffer.c @@ -0,0 +1,339 @@ +/*============================================================================= + framebuffer.c +=============================================================================== + Frame buffer functions + + Every drawing operation is applied on an internal "frame buffer", which is + simply an "image buffer" which represents the picture currently being drawn, + along with a "Z-Buffer" which contains the depth values for every pixel in + the image buffer. Once all desired drawing operations for a particular + picture are effected, a function is provided to print the current contents + of the image buffer as a PAM image on standard output. Another function is + provided to clear the contents of the frame buffer (i. e. set all image + samples and Z-Buffer entries to 0), with the option of only clearing either + the image buffer or the Z-Buffer individually. + + The Z-Buffer works as follows: Every pixel in the image buffer has a + corresponding entry in the Z-Buffer. Initially, every entry in the Z-Buffer + is set to 0. Every time we desire to plot a pixel at some particular + position in the frame buffer, the current value of the corresponding entry + in the Z-Buffer is compared against the the Z component of the incoming + pixel. If MAX_Z minus the value of the Z component of the incoming pixel is + equal to or greater than the current value of the corresponding entry in the + Z-Buffer, the frame buffer is changed as follows: + + 1. All the samples but the last of the corresponding position in the + image buffer are set to equal those of the incoming pixel. + + 2. The last sample, that is, the A-component of the corresponding position + in the image buffer is set to equal the maxval. + + 3. The corresponding entry in the Z-Buffer is set to equal MAX_Z minus the + value of the Z component of the incoming pixel. + + Otherwise, no changes are made on the frame buffer. +=============================================================================*/ +#include <stdbool.h> +#include <stdint.h> +#include <stdlib.h> +#include <string.h> +#include <math.h> + +#include "utils.h" +#include "varying.h" +#include "limits_pamtris.h" + +#include "framebuffer.h" + + + +int +set_tupletype(const char * const str, + char * const tupletype) { +/*---------------------------------------------------------------------------- + Set the tuple type for the output PAM images given a string ("str") of 255 + characters or less. If the string has more than 255 characters, the function + returns 0. Otherwise, it returns 1. If NULL is given for the "str" argument, + the tuple type is set to a null string. This function is called during + program initialization and whenever a "r" command is executed. The second + argument must point to the tuple_type member of the "outpam" field in the + framebuffer_info struct. +-----------------------------------------------------------------------------*/ + if (str == NULL) { + memset(tupletype, 0, 256); + } else { + size_t len; + + len = strlen(str); /* initial value */ + + if (len > 255) { + return 0; + } + + if (len > 0) { + memcpy(tupletype, str, len); + } + + tupletype[len--] = '\0'; + + while(len > 0 && isspace(tupletype[len])) { + tupletype[len--] = '\0'; + } + } + + return 1; +} + + + +int +init_framebuffer(framebuffer_info * const fbi) { + + uint8_t const num_planes = fbi->num_attribs + 1; + + uint32_t const elements = fbi->width * fbi->height; + + fbi->img.bytes = elements * (num_planes * sizeof(uint16_t)); + fbi->z.bytes = elements * sizeof(uint32_t); + + fbi->img.buffer = + calloc(fbi->img.bytes / sizeof(uint16_t), sizeof(uint16_t)); + fbi->z.buffer = + calloc(fbi->z.bytes / sizeof(uint32_t), sizeof(uint32_t)); + + if(fbi->img.buffer == NULL || fbi->z.buffer == NULL) { + free(fbi->img.buffer); + free(fbi->z.buffer); + + return 0; + } + + fbi->outpam.size = sizeof(struct pam); + fbi->outpam.len = sizeof(struct pam); + fbi->outpam.file = stdout; + fbi->outpam.format = PAM_FORMAT; + fbi->outpam.plainformat = 0; + fbi->outpam.height = fbi->height; + fbi->outpam.width = fbi->width; + fbi->outpam.depth = num_planes; + fbi->outpam.maxval = fbi->maxval; + fbi->outpam.allocation_depth = 0; + fbi->outpam.comment_p = NULL; + + fbi->pamrow = NULL; + fbi->pamrow = pnm_allocpamrow(&fbi->outpam); + + if (fbi->pamrow == NULL) { + free(fbi->img.buffer); + free(fbi->z.buffer); + + return 0; + } + + return 1; +} + + + +void +free_framebuffer(framebuffer_info * const fbi) { + + free(fbi->img.buffer); + free(fbi->z.buffer); + + pnm_freepamrow(fbi->pamrow); +} + + + +int +realloc_image_buffer(int32_t const new_maxval, + int32_t const new_num_attribs, + framebuffer_info * const fbi) { +/*---------------------------------------------------------------------------- + Reallocate the image buffer with a new maxval and depth, given the struct + with information about the framebuffer. The fields variables "maxval" and + "num_attribs". + + From the point this function is called onwards, new PAM images printed on + standard output will have the new maxval for the maxval and num_attribs + 1 + for the depth. + + This function does *not* check whether the new maxval and num_attribs are + within the proper allowed limits. That is done inside the input processing + function "process_next_command", which is the only function that calls this + one. + + If the function suceeds, the image buffer is left in cleared state. The + Z-Buffer, however, is not touched at all. + + If the new depth is equal to the previous one, no actual reallocation is + performed: only the global variable "maxval" is changed. But the image + buffer is nonetheless left in cleared state regardless. +-----------------------------------------------------------------------------*/ + uint8_t num_planes; + + pnm_freepamrow(fbi->pamrow); + fbi->pamrow = NULL; + + num_planes = fbi->num_attribs + 1; /* initial value */ + + if (new_num_attribs != fbi->num_attribs) { + fbi->num_attribs = new_num_attribs; + num_planes = fbi->num_attribs + 1; + + fbi->img.bytes = + fbi->width * fbi->height * (num_planes * sizeof(uint16_t)); + + { + uint16_t * const new_ptr = + realloc(fbi->img.buffer, fbi->img.bytes); + + if (new_ptr == NULL) { + free(fbi->img.buffer); + fbi->img.buffer = NULL; + + return 0; + } + fbi->img.buffer = new_ptr; + } + } + + fbi->maxval = new_maxval; + + fbi->outpam.size = sizeof(struct pam); + fbi->outpam.len = sizeof(struct pam); + fbi->outpam.file = stdout; + fbi->outpam.format = PAM_FORMAT; + fbi->outpam.plainformat = 0; + fbi->outpam.height = fbi->height; + fbi->outpam.width = fbi->width; + fbi->outpam.depth = num_planes; + fbi->outpam.maxval = fbi->maxval; + fbi->outpam.allocation_depth = 0; + fbi->outpam.comment_p = NULL; + + fbi->pamrow = pnm_allocpamrow(&fbi->outpam); + + if (fbi->pamrow == NULL) { + free(fbi->img.buffer); + fbi->img.buffer = NULL; + + return 0; + } + + memset(fbi->img.buffer, 0, fbi->img.bytes); + + return 1; +} + + + +void +print_framebuffer(framebuffer_info * const fbi) { + + uint8_t const num_planes = fbi->num_attribs + 1; + uint32_t const end = fbi->width * fbi->height; + + uint32_t i; + + pnm_writepaminit(&fbi->outpam); + + for (i = 0; i != end; ) { + int j; + for (j = 0; j < fbi->width; j++) { + uint32_t const k = (i + j) * num_planes; + + unsigned int l; + + for (l = 0; l < num_planes; l++) { + fbi->pamrow[j][l] = fbi->img.buffer[k + l]; + } + } + + pnm_writepamrow(&fbi->outpam, fbi->pamrow); + + i += fbi->width; + } +} + + + +void +clear_framebuffer(bool const clear_image_buffer, + bool const clear_z_buffer, + framebuffer_info * const fbi) { + + if (clear_image_buffer) { + memset(fbi->img.buffer, 0, fbi->img.bytes); + } + + if (clear_z_buffer) { + memset(fbi->z.buffer, 0, fbi->z.bytes); + } +} + + + +void +draw_span(uint32_t const base, + uint16_t const length, + varying * const attribs, + framebuffer_info * const fbi) { +/*---------------------------------------------------------------------------- + Draw a horizontal span of "length" pixels into the frame buffer, performing + the appropriate depth tests. "base" must equal the row of the frame buffer + where one desires to draw the span *times* the image width, plus the column + of the first pixel in the span. + + This function does not perform any kind of bounds checking. +-----------------------------------------------------------------------------*/ + static double const depth_range = MAX_Z; + + uint16_t const maxval = fbi->maxval; + uint8_t const z = fbi->num_attribs; + uint8_t const w = z + 1; + uint8_t const n = w + 1; + + uint8_t const num_planes = w; + + unsigned int i; + + /* Process each pixel in the span: */ + + for (i = 0; i < length; i++) { + int32_t const d = round(depth_range * attribs[z].v); + uint32_t const d_mask = geq_mask64(d, fbi->z.buffer[base + i]); + + uint32_t const j = base + i; + uint32_t const k = j * num_planes; + + varying const inverse_w = inverse_varying(attribs[w]); + + unsigned int l; + + /* The following statements will only have any effect if the depth + test, performed above, has suceeded. I. e. if the depth test fails, + no changes will be made on the frame buffer; otherwise, the + frame buffer will be updated with the new values. + */ + fbi->z.buffer[j] = (fbi->z.buffer[j] & ~d_mask) | (d & d_mask); + + for (l = 0; l < z; l++) { + varying const newval = multiply_varyings(attribs[l], inverse_w); + + fbi->img.buffer[k + l] = + (fbi->img.buffer[k + l] & ~d_mask) | + (round_varying(newval) & d_mask); + } + + fbi->img.buffer[k + z] |= (maxval & d_mask); + + /* Compute the attribute values for the next pixel: */ + + step_up(attribs, n); + } +} + + + |